Probably a little bit of everything, no telling how advanced the AIs were when randomized, and any civ can have a bum start position which it is harder to get out of without tech trading. I consider the exploitation of tech trading as one of if not the most powerful strategy available.

On the higher difficulty levels, if I turn tech trading off and don't play the diplomacy gambit I'm very likely to get creamed. Maybe it's just habit, but I even went diplomatic playing the Yor when I was getting far behind on tech / military and such on masochistic and in a few months I was back on top in tech, economy, military and almost everyone in line to be my ally if I wanted, but I destroyed them instead.

It also depends on what your style of play is (for that game) as tech trading on makes playing a good, diplomatic race excessively easier while tech trading off favors the militaristic aggressors. One way, you sit back just research diplomacy techs and let everyone else give you a free ride to the top. The other way, you can focus on weapons and invasion which your enemies will often lack, then when you come to conquer them, you get their domestic techs for free.

I've also found it fun though to try to be diplomatic with tech trading off and trying to be evil with everyone working to their best against me, but as I said, on the higher difficulties it's not really an option for me unless I want one of those wounded in action medals... which I do hope to get soon.

I also find it fun to do other odd things like a tech victory as Arceans on a tiny galaxy. I guess I'm just wierd like that, but I'll save that for another thread.

I'm playing my first 1.1 game with no tech trading and I'm a little bit torn. In principal I like this option; it always bothered me before that the races could be so similiar militarily, obviously through tech trading. But with tech trading off, there's little reason to interract with the AI so I feel that I'm missing out on a lot of the diplomatic side of the game. Maybe there should be an option of no trading of military techs?

In these types of games, I'm really big on technology. You can have your big military, strong economy, or superior production, but I want first place in technology. I prefer a small but intimidating navy. The only problem was that the only way I could get ahead technologically was if I did more than half of all the research in the galaxy. By myself, I could research five technologies in a given time. But the six other races would research their own tech and trade with each other. I would be doing more research than any one race, but since everyone would trade techs, I was left behind. .... That's too bad. The only way to counter this was to do more research than all the existing races combined. That would take a while.

"Why don't you just trade techs with them?"
That's a very good question and it deserves an answer. I didn't like paying hundreds or even thousands of credits for each technology I didn't have. I also didn't want to give up one of my unique technologies. "No I will not give you advanced logistics for stellar cartography!" "Shields III for Chaff? Are you mad? Do you think I'm mad?"