It's going to take a while to review, they all have flaws... for example; Atoll: if you try to hire/revive hero at traven, hero get stuck in tree. Fallen Fortress: I thought it's going to be good map, but starting off a base is a clust (night elf, be very afraid). Fire and Ice: A recent map submitted, I thought this could be good map, but the problem is fighting space is too small.
I suspend that Serpent Canyon is going to win because of it's use of textures on level, map design, good fighting spacing, good use of props. I didn't try all of map so don't take my word.