From what I've personally seen, tgh has a lot of maps, but we usually only play on a minority of them. In terms of which server, tgh or poketrade, should get the map, I think that poketrade should get it, as it has a lot smaller choice of maps than trade gaming history does, and the community has explored the ideas of adding quite a few new pokemon maps. So far, nearly all of the pokemon maps have been very unbalanced, one-sided, made only to be accurate to the games they're from instead of incorporating balance into them. TGH can always get more gaming history maps, since lots have been churned out.
tl;dr - poketrade because most of the maps we tried have sucked