Since we are talking about ctf4 and ctf6, I thought I would offer my opinions as I don't see anywhere else to do so.
Ctf4 is pretty good. It doesn't have too many pickups near the bases so with more than 2 players on a team, the player carrier will likely have to wander into the middle to get weapons, and I like this. My biggest problem though is with the odd movement once you gain any speed. I might just have a hard time adapting but I don't think I have ever moved from one end to the other with any kind of speed without hitting one of the many bumps. Again, that could just be me.
Ctf6 on the other hand is some piece of work. Entities are oddly placed which leads to ultra slow movement. The pits are horribly placed over the bases and it is very easy as a defender to simply hook an attacking tee straight into them. Overall the movement is really awkward with the weird tall center section. If I have to find myself making that big agonizingly slow hook up around that hill in the middle one more time I will go crazy. Simply put, the upper path is massively more advantageous than the lower path but the problem is that in order to get to the upper path you have to hook upwards at angles causing slow movement. And I question how well this map holds up for many tees which is what it is intended for given the lack of weapons and sheer width.
There is a good reason why barely any of the several hundred servers right now are using ctf6 and it's not that the map is new because ctf4 is competing with current maps for medium sized games.