Depends- I had a high LSAT, lower gpa (product of laziness not inability). I did not get into a couple schools that are gpa whores (UCLA & Boalt). I also was WL at another school & then they ended up needing high gpa ppl to bring up their stats, so I was SOL. Also, high gpa you can put on your resume.
As far as law school success, I don't know which is better- I would argue LSAT but I am biased.