This is just my personal opinion, but I prefer Logic Pro 9. I have both, and work the majority of the time in LP9. Having said that, I know that much of the reason is due to the fact that I'm familiar with LP9 and I felt that LPX seemed a bit "clunky" to me. It didn't respond to my touch/commands in the way LP9 does.
Truthfully the differences are negligible, but I liked LP9 fwiw. Save your money unless you feel compelled to update!