if you are just starting out use the basic maps for 2-4 players. They are plenty aggressive. The other map variations require different strategies and shift the balance around. If you are just learning I wouldn't use them yet.
I actually got to play Singularity finally a few weeks ago. It almost ended very quickly, with one player nearly wiping everyone off the board with his battleships. It ended up being more on the short side of medium, with one player pulling ahead pretty easily with Strategic and just a wall of his ships moving across the board in a sweep.