The original Radius shape is very slightly different from the JS
body shape- i guess it's slightly smaller or something. However, I guess there was an overlap after the JS
was introduced and before the R-series was discontinued, and i guess during that time (or soon into it) the R budy was changed to JS
specs. The difference is very subtle, though, and unless you're A/B'ing with a Satch, you'd probably never notice the change unless you were VERY familiar with the satriani design ( i own neither, so i'm just going from playing experience with my friend's chrome Boy and a few unmarked used Ibanez R/JS
style guitars that could have gone either way).
Pricewise, a used R-series with comparable specs to a JS
-1000 (edge, two humbuckers) will most likely be less than a used JS
, and certianly less than a new one. Of course, once you factor in the cost of replacing the pickups to PAF/Freds (or similar quality pickups if you want a slightly different flavor) and rewiring it to a 3-way selector with push/pull tone and high-pass filter controls, you might be better off going with a new JS
, especially as the post-98 (i believe) ones have a digitized multi-radius neck that'll allow you to get slightly lower action out of the thing. But this will probably put you into the 8-900 range, so if you're willing to take a dead-stock R-series, that'd be the better bargain- of course the dimirzios will smoke the stock pickups, and the switching won't be the same, but as far as stock pickups go Ibanez aren't all tHAT bad, and the switching might be nice for the novelty. Your call.
Of course, i didn't really answer your questions, did i?