No offense, Wiley, but you can't read peoples' minds, so possibly you mean in your mind? "To you" that's the case. The TA has all the action in one area. The melee arena has most of the action centered in just a few sectors. The empty spaces in big maps only serve to make it seem less populated, sometimes. It's all very fluid and depends on many factors.
For anybody wishing to test the waters with 2-sided teams in custom arenas, look at the maps the AvA arena uses -- they often use custom maps with 1 side disabled or minimized for setup purposes, and it might save you the trouble of creating your own terrain map.