I have to agree with CelL ; but I still think Zaitox is a bit unfair because of the one way to the base. This can be quite irritating for the attackers, and I know how this feels.
I don't have any problems with Semi, although Semi isn't one of my favourites. About that red is better in Semi... ye, you can camp under the blue base and hit the opponent. Unless he/she takes another way and is fast enough, of course. The Marshland of Evil is a good 3v3 level. Jungle's Edge is a bit overplayed, but not really. Semi is played more times. And about BBLair... well, BBLair is overplayed, and I find the PU placement biased. The RF doesn't respawn all the time there, even when respawn is on.