X25 is going to have the best wakeboard wake. No question. If you are a VERY serious wakeboarder, there is only one choice here.
X30, X25, and X45 all have great surf wakes. I have never surfed an X35, and have never heard much about the surf wake behind it.
Biggest downfalls of the X25 and X35 are the handling. They are excellent in rough water, but they do not handle nearly as well as the X30, or even the monster X45.