Both have what are considered world class wakes. I cannot personally comment on the X-Star wake as I have never been behind one. But I think that again we are talking about different classes of boats. The X-Star is almost in a class of its own due to price. Boat show price here for the X-Star(w/L-18) was 22 K higher than a Air 210....
So with that said, it being a much bigger boat with better storage, regardless of wake(IMO, personal choice and whatever you have, you adapt to and it becomes your favorite)....if someone was to say, I'll give you a new X-Star or SAN....I take the X-Star.
Again....in the Mastercraft line....the X-2 is the comparable model to the SAN. Other opinions may differ.