I'd approach that question from two angles.
First, three blades are generally bow lifting props. That may get you a couple miles per hour on a heavy boat that requires all of the trim to get to full speed (and are still pushing water). Allisons have a lot of lift built into the hull, to the point that full trim is detrimental. You may only run 75% up on the trim to get the boat running clean and free. Additional bow lift is not really necessary, so the three blade may not net you much. If anything, only a mph or so, instead of bigger gains that you might see on a lead sled.
Second, if you can run 95 with a 4 blade and have great holeshot and turn on a dime without the prop losing bite, why would you sacrifice the handling to run 96? Not much on the water is going to pass you at 95, and anything that can pass you at that speed is going to get you at 96 too.