I've ridden both over 100 times.
I believe that if you look up the figures, JPRA is actually a steeper/higher drop than Splash. However, since in JPRA you are in a larger boat and you don't see the drop until you are already going down it it doesn't feel as big. In a two-by-three seating arrangement at Splash and the view of the Castle, etc., Splash may actually feel more "scary".
For the OP who wanted to know about JPRA, yes, it's much shorter thank Splash (and shorter than the version in Hollywood as well). It goes like this :
1) Ride through JP gates
2) Outdoor lagoon with brotosaurus, etc.
3) Hammer-headed dino pushes you "off the track"
4) Approach "restricted" area - sometimes the spark effects are down here, raptor cage above the tunnel
4) Upward tunnel bringing you into building, several dinos on the way up behind the chain link fences (sometimes they are down as well - it's almost more creepy when they are just back there, barely visible in the dark, LOL)
5) At the top of the climb the spitting dinos squirt you
6) You turn the corner, T-Rex is there
7) Drop
It's pretty wham-bam-thank-you-t-rex. I do love the ride, but it's nothing compared to the artisry of Splash Mountain.
As to the wet factor, yes, you usually get more wet at the end of JP - the added weight of the vehicle makes the splash bigger. I actually get more wet on Splash during the ride than at the end - at several points (like the drop into the the laughing place) the backwash tends to come over the front of the log and onto my lap.
N.E.D.