I joined a couple of Ancient Med and South America games - the maps look interesting and are not so unbalanced actually - but obviously there's a learning curve until people get to understand the map better.
For South America - the map is brutal - small and you start fighting first turn already - the feeling is as if everyone is playing AUS :)
Hence, results are random, luck will play a bigger role, and so will metagaming (a 2-way alliance can win the game in 3 turns if they are not caught). Brasil is really terrible to play (big like RUS, but with only 3 centers and positioned in the center)
For Ancient Med - the map is quite big (34 centers for 5 players, compared to 24 in the SA one) and allows for reasonable expansion even if you fight. Great map for people who love the tactical aspect of the game - movement, positioning and logistics are key for this one. I like it a lot :)