I had a 2011 and 2012 both with 6L engines. The Latter had the Ilmor. To speculate, I would guess that if your X2 had a 5.7, and assuming the X25 has a 5.7, the X25 will feel more sluggish due to the boat being much heavier.
When I went from a 5.7L Moomba LSV to a 6L X25, I noticed that the X25 was powerful, but not quite as nimble as the LSV - again probably due to weight.
I have never tried an X25 with the 5.7 so I can comment for sure. Good Luck, you cant go wrong withan X25