Skornflakes --
Heh. My suspicion is that, depending on your play style, small maps may be HARDER than larger maps. For instance, in this genre I tend to play as a builder / researcher early... and therefore I'll tend to lag militarily early on. In a small map you're more likely to run into neighbors fast, which means that military parity becomes more important.
On the other hand, if you're a blitzer by nature, small maps may indeed be easier -- although in GalCiv, since it takes a while until you can even build combat transports, and there's neither telepathy nor orbital bombardment, blitzing is still harder than it would be in, oh, MOO2.
Some random bits:
There's two types of trade in the game. One is the usual Civ-style deal-making, where you can haggle over techs, ships, treaties, et al -- e.g. you can even say "Hey, I'll attack these guys if you pay me this much". You should frequently enter the trading screen with everybody you know, at least so you can monitor what technologies they have that you don't, and so you can check up on their attitude towards you and others, and how dependent they are on you.
The second type is using trade routes, i.e. freighter traffic. Trade routes bring income to both players, which means that you can eventually be responsible for a significant percentage of somebody else's income, which will tend to make them like you.
A weird bit about long-term purchases ("leasing"): There's a random event about increasing corruption in the galaxy. If it appears a few times and each time you choose the Evil path -- that is, "who cares how they make money, so long as they give me a cut" -- your Interest Rate ability may get so good that it's much CHEAPER in total to pay Mitrosoft than to do a 1-turn purchase. But otherwise long-term payments can and wil hurt you...
Stardock Forums
It's always a Diplomatic or Space Race victory.