STP is definitely the best as far as I'm concerned, it's just a damned good record. The styles vary, but I think the songs go very well together, the song order well thought-out. I think that GH is more dramatic in its varying styles in that sense.
SL is just a bore to me. Why was Summer of Love left out, it would have been the best track!? I like the title track and songs like Tupelo, which is fine, but in the end it just kills my spirit. Gimme RPD with its wonderful grooves any day of the week.