I played Floodzone for a while last night, but I can't say that i really enjoy it that much. It's such a wide open map that it really seems to favor certain classes over others. A good sniper can have a field day on it, and a scout is quick and nimble enough that he can usually use his speed and the open ground to get in close enough to do damage. But, I feel that the slower classes such as Heavy and Soldier really suffer as it's hard for either of them to do reasonable damage at such long ranges. Not to mention Pyros and the fact that there are few places to put an SG where it won't be taken out at long range by another class.
Now Chaos, on the other hand, is a fun map. The cap limits are a little low so it can make for some very quick games, but it's tight enough that the action is usually pretty fast and furious and just about every class can be useful. It feels much better balanced than Floodzone to me.