On My X-30 I went form the 14.25x14.5 to the 15x12. We mostly wakeboarding with 3k. Time to plane was almost cut in half, RPM's went down by 200 and so did the fuel useage. Win win to me. I felt the prop made a bigger difference than going from the 5.7 to the 6.0.
Top speed is around 36 now. But that's not at all important to us either.
2013 X-30, 6.0L with 2500lbs of ballast and 500 lbs of lead.