Trading techs can be a highly advantageous or disadvantageous area of the game for players. This section will help explain how to get the best end of the deal you can possibly get. First of all, before explaining how to get the best end of the deal you can get, the system driving tech trading needs to be explained and analyzed. The system itself is pretty simple. When you engage the foreign race in diplomatic talks and you go into the "Exchange Technology" area the game will pick out a list of techs pretty randomly based on what it has that you don't have.
If the number that it has that you don't have is large, the randomness occurs at the moment you hit "Exchange Tech" and not at the moment you start diplomatic talks in general. What this means is that you can go into the exchange screen, not see anything you like and back out of it, then go back in and you might get a different set of options.
Something that is important that drives the entire system is that the opponents will never accept "fair" trades. Each tech has a level in the tech tree that determines the cost to research it and the opponents will pretty much never trade evenly, especially when you ask for it.
If the computer asks you to trade, generally it will be a little more generous and might offer a fair deal or one advantaged to you. This is extremely hard to test and verify. A few players report having got the good end of the deal before, but at best it is going to be one out of 100 or so entire games due to how seldom the computer solicits its own trade requests.
The opponents will not ever offer you anything that they are not willing to trade you for stuff that you have. Usually the margin that they want is pretty substantial. They might try to reach for something as far as 10 or 15 tech levels ahead of their tech, but if you have enough stuff with a shorter margin they probably wont.
This pretty much means that you shouldn't expect to get a whole lot of cutting edge techs from trading. Trading is more often going to help you fill in the blanks of low level stuff you didn't get rather than helping you to get farther ahead of where you are now.
That stuff said, you can still get the better end of the deal on tech trades because the computer really doesn't have perfect programming in terms that relate directly to the game state. The game will try to be stingy with certain techs that it thinks are very important and make you suffer a lot of pain to get them. Those techs are few in number though, most are just handled completely randomly based on what you have that is higher level than the tech you want.
One set of techs that this specifically applies to are the Inertial Stabilizer and Inertial Nullifier techs, the computer tends to massively overvalue these. It overvalues them when it wants to get them from you and when it offers them to you. No idea why, they aren't that overly awesome for a large part of the game. They tend to be quite large for their benefit and they are best used when your built in maneuverability is already maxed, which it often won't be due to space concerns. Those same space concerns force you to leave off the inertial devices themselves as well.
The thing you want to keep in mind in all of this is that an upgrade to the economy is across the board and an upgrade to something relating to ship combat might not be an upgrade at all. Generally, the only trading you want to do is trading ship techs for non-ship techs.
The Ion Cannon is a level 11 weapon and Terraforming + 20 is a lvl 9 Planetology tech. If you can make this trade at a time when you don't already have Terraforming + 30 or above, you should take it. You might or might not have Terraforming + 10 already by this point, but say you do. Say you are still on Robotics Controls 2 (the worst case) and that you aren't the Meklars (the worst case).
Going from +10 to +20 in this case would allow you to get 10 more population units and two more factories per population unit. The population units will be doing about 0.5 BCs worth of manual labor per turn and each factory will be creating one BC worth of production per turn. That is five BCs from population units and 20 BCs from factories. That means your increase to each and every planet in your empire, once the tech is implemented on them, will be up 25 BCs. That number times a dozen planets in your empire times a dozen turns is a massive total in terms of production.
If you are the Meklars, if you have increased Factory Controls, or if you have Artifacts or Rich worlds, the value of these Terraforming technologies gets even higher. On poor and ultra poor worlds, a lot of the production comes from population so having more raw people on these worlds is quite helpful as well.
The benefit they will get from that Ion Cannon is a lot more difficult to see. If it is their new best weapon it will probably take up a ton of space and it might be hard to see why one of those is better than two of the next lower weapon, a strong consideration.
New weapons tend to take up so much space on ships that it is often better to devote most of the space you have for weapons to the lower techs that have been miniaturized and with which you are able to put a lot more into the same space.
If you are giving them old weapons, the deal is even worse for them. They might get something they can load up in massive numbers on their ships, but you might have shield technology that completely obsoletes it anyway.
Compare that to the huge benefit that you get from having 10 more population on each planet in your entire empire, a benefit that gets better each planet you have (having more is what you want anyway) and which can't be obsoleted by anything the enemies research.
The thing to keep in mind when trading techs is that your economy is what wins you the game. Advantages in economy translate to advantages in tech which translate into winning fleets. Their economy, on the other hand, is what wins them the game. If they don't have a winning economy, they won't be getting ahead in tech and they won't be constructing winning fleets.
In trading, always choke their economy first and foremost. There are other techs that relate to ships that you should never give them, such as High Energy Focus. Make them research that on their own when they get around to it. Most ship stuff, though, like Inertial Stabilizers is something that benefits more the person with the better economy anyway.
If you give them the Inertial Stabilizer for something useful in terms of economy and they load it up on their ships they are going to be taking something else away and at the same time your economy is bigger so you can just plain put out more ships, negating some, if not all, of the advantage of the device. The net plus will probably be to you.
If possible, the stuff you always want to trade for is
- Robotics Controls Technology
- Terraforming +whatever Technology and Complete Terraforming (+120)
- Reduced Industrial Waste Whatever% and Industrial Waste Elimination (100%)
- Ecological Restoration Techs
- Environment Improvement Techs (Soil Enrichment, Advanced Soil Enrichment, and Atmospheric Terraforming)
Additionally, stuff to upgrade your missile bases can be really good too, but you really want to watch what you give for these, and not give too much.
- Duralloy / Zoritum / Andrium / etc. Armor
- Class V / X / XV / XX Planetary Shields (especially 5!)
- Class Whatever Deflector Shields
- Any advanced type of missile Hyper-X / Stinger / Mercullite / Pulson / etc.
The Gauss Autocannon is about the only weapon worth trading for unless you are way behind in weapons tech or you are massively deficient in some area of weaponry (like Bombs or Missiles).
Environmental controls techs are not worth getting unless you have worlds in range that require that technology to colonize and you think you can get there first after you trade for the tech and you think you can hold the planet. Usually, because of these conditions, its not worth it to trade for the tech. Usually if they have it and you don't they will just colonize the world before they offer the tech up in trade.
That being said, the added benefit of environmental controls is that you are able to invade worlds with people that are that level and below. Even if you have no hostile worlds around you, it can be useful to be able to send ground units into, say, dead and inferno planets that other people control. You won't usually need this capability right away, but keep this possibility in mind for later in the game.
Another extremely important area of consideration is in regards to techs from the past that don't even necessarily give you any large benefits. Something like Battle Computers Mark 4 being offered when you already have Battle Computers Mark 5 (or higher). All it will do for you to get this tech is add 1 to your level of research in the Computers field. Specifically for the computers field, that will give you a 1% bonus to all spy attempts you ever make in the future.
Something like Industrial Tech 7 when you already have Industrial Tech 6 is pretty much completely worthless except for a very small increase to construction technology miniaturization. If the enemy wants your Tech 7 when you know they have Tech 6 and you can get something useful for it, you should take it without question. You should never try to give anything even remotely useful to the computer for something that will just give you a small benefit in terms of miniaturization.
There are three more factors of note:
- The size of the opponent currently.
- Their potential to trade away your tech for something they do need.
- The "you against them" issue.
If the opponent is very small, as in the case where they are less than even a third of the size of the next lowest opponent then you can probably trade them stuff without losing too much sleep over it. Opponents try to beat other opponents and usually they won't trade away useful techs with each other. That being said, the computers will spy on teach other and try to steal each others' techs, and small empires are especially hurt by this.
The safest plan is to trade away nothing that will measurably help anyone. The second safest plan is to only trade stuff that you don't care if everyone gets, and the most risky plan is to trade stuff away and hope the tech isn't stolen or traded away. Your tolerance for risk measured against what you get in return is going to set the bar on whether you should go ahead or not. The more risky players will make the riskier trades more often and sometimes they will come out ahead and sometimes it will just cause them pain and suffering, that is the nature of risky play.
In terms of the "you against them" issue, and this goes back to trade treaties, is that you are being measured individually against every other race individually. If there are five races in the game and two of them benefit, then they are both comparatively ahead against the other three, even if they gain nothing comparatively against each other.
If you are #1 in the galaxy and you trade with #2 in the galaxy and both get something quite useful in the trade, they both become a lot farther ahead than #3, #4, and #5. This can allow you to "cement a lead" that you have.
It is also possible that the #1 is so far ahead that everyone else is fighting for a distant second. It is possible you could then trade with everyone that is not the #1 player and even though you may lose ground to each one individually, you may gain ground as a whole against the others because you gain maybe three or four times and they each only gain once. They might gain more individually than you gain, but your total gain will be greater at the end of the trading session.
If you are almost or fully dead last, trading can almost never hurt you because the last thing you want to have happen is for the current positions of power to become cemented the way they are now. Any trade you make with anyone will put you comparatively closer to being relevant in the galaxy under these conditions. You might as well trade everything you can and hope that you at least get lifted out of the last or almost last space as a result.