turbine is excellent because it has the middle section that is completely open and one team can fight to take control of that
it also is virtually impossible to lock down the intel room with engineers, and the only people that say it is i guess have no idea how to play demo or even heavy (as ive destroyed 2-3 sentries as both classes even without a medic)
if youre gonna do a competitive ctf map dont make weird alt routes just make it straight and to the point, like turbine
2fort is probably the best ctf map valve has made to be honest, mostly because its somewhat small and very straightforward
both sawmill and doublecross are incredibly awful, and ctf_well would be a lot better if the intel room wasnt gigantic, because with that you can put a zillion sentries all over the place