Splash Mountain is my favorite ride! Someone previously mentioned if you sit in the back of the log you get soaked, I disagree. I've sat in the back quite often and I rarely get wet, my last trip I kept getting put in the very front of the log and I got Soaked! One time at the big drop the front of my log I swear dipped in the river and water poured over my head, it was like a shower only all the water at once and FREEZING! It was AWESOME! But I still prefer the back.
GRR is awesome as well. I do recommend a poncho because you never know if you're gonna get soaked or just wet. Both are great rides, have fun getting wet!