I'm just thinking a larger map might generally have more resources available, to either obtain myself or to trade for. Is scarcity something that changes with difficulty level?
My most recent game had me trading for uranium. Monarch/Tiny/Continents/Germany vs. Spain, Carthage and India. Only Spain had uranium, 3 of them. They traded 1 to Carthage, and refused to trade to me once the Space Race began. On top of that, Carthage got the drop on me and was loaded up ahead of me, even though I had the tech lead (it took longer for me to build Apollo). So I built everything I could, then attacked Spain at the last minute and held the uranium for all of one turn - just enough to start building the last part in 2 turns to eke out the victory. (It helped that Carthage did not yet have Robotics, of course.)
I was originally planning for Domination, but I waited too long to start and it became no longer feasible, so I switched gears. This has happened to me a lot once I started playing Regent ... mostly Spaceship wins. I haven't figured out how to get a military edge on the AI yet, even difficult at Regent.