The biggest map and the best map for glitching are different from eachother. The best glitching map is probably Warhead. But the biggest map is probably Snow Valley or Waverider. There aren't that many Snow Valley glitches because the world is completely gone underneath with no way to get into the mountains, although the same could be said about Cold Seed but you can get into the mountains there, it's awesome.
But yah best glitching map = Warhead
Biggest map = Snow Valley.
I do know one snow valley glitch that awesome you can't die and get a 180 degree view of the map.