Today I tried two guitars in my local store, an rg350dx and a sz230mh, both Ibanez. I liked the sz's thick tone, but the rg played faster. I think the string action was maybe just a bit lower (changeable), but I know the neck was thinner (not changeable) which I will look at next time I go. The rg just felt better in my hands. But really, which should I go for, tone or playability....or maybe some different guitars that are faster than the sz, still have the chunky tone?
doesn't a huge amount of tone come from the amp ?

i would go for playability.... other wise you might get pissed off playing something not as swish.
a gibson sg is kind of a slimmed up les paul that might interest you or maybe like an esp v-200
choose playability over tone. Most of the tone comes from your amp anyway, and if the guitar is really sucking away you're tone you can do a pickup swap. A guitar should feel good to play above all, you can have great tone but if the guitar just doesn't feel right you'll get annoyed by it and it'll hinder your playing.
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well, the guitars actually did have a very different tone (tried them on same amp with same settings), as the rg is made of basswood with a bolt on neck, and the sz is made of mahogany with a mahogany set neck.
Playability is many times more important than tone for me, especially since tone is subjective and no tone is really better than another, they're just different.
I'd take playability over tone anyday.
My SG sounds good, but I can barely stand the size of the neck.
Also, tone is more tweakable than playability.