I have an '82 360-12BWB. Hub & mark have pointed out the essential differences, the most critical the 360 semi-hollow vs. 620solid.
The neck/fingerboard is indeed narrow, whether or not 12 strings are crammed accross it as on mine, and unless your fingertips are particularly thin, learning to play alternative or altered chord fingerings/voicings, or how to be most conscientious in 'getting up on your tips' and not laying the tips lazily across strings is probably going to be something you'd need to be willing to deal with. That is, once you've gotten to actually try one and see how it fits. They do make a couple of models with 1/8" wider boards, notably McQuinn & Petty signature models (because those guys asked for more room and could afford it.)
24 vs. 21 frets? Beats me. I don't think I've ever wanted or needed to go past the 18th fret in my life. OK, 20 maybe a couple of times.
Some don't care for the Ric's glossed fingerboard on these. There's a good, practical reason for it, and does influence the sound and playability. Not worth debating. If it's a hangup, walk away from ric and don't look back.
Ric's vol & tone pots are wired/placed a little 'eccentrically', but logically once you get used to them. Make note also of the smaller, 5th control knob: it can function 3 different ways depending on how you have the vol/tone pots set on each pickup, which position you have the 3-way toggle in...and finally, if you've got a model with the optional 'Rick-O-Sound' stereo wiring scheme, as mine does, with the proper cable (Stereo jack to 2 mono jacks), this alllows you to throw each pickup into a seperate amp or channel, and/or or fx pedal or chain. And the 5th knob works a bunch of voodoo in that mode.
You'll also want to check to see if the one you're spotting has got hi-gain or more 'vintage' (lo-gain single coil) pickups. Mine has true vintage 'toaster tops'. These produce a clean Ric sound/tone that most Ric players describe in the Dylan-esque term: jingle-jangle.
Love it or hate it. Not much gray area. That's the way it is with Rics.