Depends on the boat and boating you do. I have 07 X2 and run a 14" "torque" prop on the inland lake I keep my boat on most of the summer. It's perfect for wakeboarding and surfing and the boating I do on this lake all is short distance. I have access to a slalom boat so I don't need high end speed to ski while I'm on this lake.
I have a 13" prop I use while I'm on Lake Erie. This "speed" prop gives me better range (fuel economy) and top end speed for slalom skiing should rarely seen calm water conditions and the desire to take a slalom run in the big water materialize. Or for a run back to the harbor should conditions turn bad out of no where as Lake Erie is known for.
The 14" prop is where it's at when surfing with a boat load of friends on the inland lake. I will say that on the big water the 13" prop feels much more balanced for the boat without the surf set up. Having both props allows me to set the boat up for the type of boating and type of lake that I'll be on.