the RG is for metal, strat has the best quack, yada yada yada...
i own both Ibanez & fender, it's best you own both really, if fender can replace ibanez entirely, the Ibanez company would have closed shop & maybe sell sushi instead.
IMO the 'RG for metal' association has to stop. it would have been a valid reference if we were all trapped in the '80s, but that's not the case. there are many uses for the RG, it's just that we are more exposed to the metal orientation eg: Mick Thompson recently endorses Ibanez.
the RG also offers different neck profiles for various models, 'thin' is a summary for those who can't differentiate these profiles. i wouldn't classify the 'Ultra' neck (RG 2620) as 'thin'. also, neck profiles has got to do with personal preference most of the time; Paul Gilbert has big hands but he won't play anything else but ibanez.
i'm not here to offend anybody but Ibanez/ Fender/ Gibson/ etc are offering tools for you, you choose...
blahblah: your '70s strat has a nice ash body yes? i'd rather you keep it & save for an Ibanez instead... if you choose to sell it off, then no RG would be able to pull off a typical, strat single coil tone- zilch. unlesss you are sick & tired of single coils of course...
why RG5XX & not any of the current offerings? Prestige Ibanez?