The Verado is more reliable then the Pro Xs. the reason the pro's use the Pro XS is its about 150 pounds lighter and the Pro XS is faster by 2-4 MPH. The Verado guys off shore get 3-4 thousand hours out of their Verado's. The bass boat guys rarely run more then a few hundred in a life time. The 4 strokes are good motors just hard to justify the extra money or weight, off shores boats are not weight sensitive. just my .02
The other obvious reason is no 2 stroke oil.
The most important part is the price difference. When you're flipping boat yearly the pro xs helps!! I always noticed the lack of mercury engines offshore or on the coast. Seems like the guides/fisherman went with Yamahas or Suzuki/ tohatsu. The Hondas are absolutely the worst when it comes to salt water corrosion.