It's funny. I'm slowly coming to the realization that I enjoy playing the SRX more than I do the (twice as expensive, Prestige) SR. Ergonomics-wise, both are a dream to play, but the SR is clearly the better bass: lighter, with better contours and a ridiculously fast neck (I've said it before and I'll say it again, I have yet to play a better neck than the Ibanez SR). The only exception is slap, which the SRX's wider string spacing makes much easier.
However, when it comes to tone... Well, again, both are great basses, but the SR's sound is too modern for me. It's super-clean and versatile (especially now that there's a working preamp inside), but the SRX has a natural, vintage growl that lands somewhere on the Jazz/Stingray axis (only a tad less bright because of the neck-through construction), and I really, really dig it. I gotta give major props to Ibanez on this one: their Alnico PFR pickups work remarkably well.
(semi-related: I'm starting to think that maybe my ultimate dream bass is a Sadowsky, Sandberg or other "active Fender Jazz only with ergonomics that don't suck" bass)