Everything, ships have same names completely different shield mods though, races have same names, but completely different income styles for the most part.
you have to feed people here or they die, there on UC they just take a pay cut.
Here if you get out of debt can`t really get bailed out of it by random tribute, so best to stay out of debt since a restart here means a full restart, you lose everything here on a restart. on uc when you restart you lose a percentage of things only.
uc has a more advanced battle scheme, and some gc players will deny this is true, but its a fact, battling can be more difficult there with out a fed to support you.
however apart from that its a much simpler game, making cash is a cake walk, and i defy anyone to say otherwise, making cash on uc is simple and really its kids play.
on GC you actually work for it, and because you work for it, it therefore means more to you as a empire and a individual, you don`t waste resources randomly you plan more strategically on gc, and that`s always going to be why some prefer GC and its most certainly why i love gc more.