I've 5 different RGs and the necks on 4 of them are completly different.
1. 1998 J-Custom RG 1802 which has the Ultra neck which is deeper then the rest, 3-piece and has the Volute behind the nut rather then the Scarf jointed headstock. I really like this neck it's the biggest neck of any Ibanez RG (excluding 7 strings) I've played but it's still thinner then your standard strat. Satin finish so feels almost like raw wood.
2. 1990 RG USA CUSTOM Which has an original Wizard, Very thin and fast, quite a thick laquer but over all also a very nice neck.
3 1989 RG 570 and 1992 RG 550 I believe these are Wizard necks also. these has necks which are practically identical, cept one is rosewood board and one is maple board, roughly about the same depth as the USA custom but doesn't feel exactly the same, Fairly Typical Ibanez neck that you'll get on 90% of RG's you'll see.
4. 1996 RG 270 This one is my personal favourite size/shape, it's a little fatter then the Wizard so I'm guessing that it's the Wizard II, I've sanded the finish right off the back of this one and It just feels great.
5. I've also got a 1987 540 S which is supposed to has an original wizard but it seems much thinner then both the USA Custom and the 550 and 570, thick laquer.
I think the fatter necks do contribute to a better tone, the J-Custom is the best sounding guitar and the 270 has the best feeling neck and they're the two with the fattest necks.
All these guitars can be seen here http://www.ibanezregister.com/Galler...ip%20joyce.htm