well, it depends on your taste. All of those guitars are very well suited for metal. RG’s are shredding guitars. They have those floyd rose trems and pencil thin necks for shredding purposes. if you are a big lead player, I would go with the RG 550 (the higher the number, the better the ax) look for the V7 and V8 pickups. I think the S models have those same pickups, otherwise they have the AH1 and AH2, which are just as good. The S models have 22 frets instead of 24, and a thicker neck. I think the tone is better on the S models. I also think S guitars are much more elegant looking, but that is just personal taste. Another guitar you might want to check out is the JS100 (the satriani model) those are pretty sweet. If it was me, I would go with the S 520, but it is not me. Try them all out and make your own decision.
RG – crunchy lead guitar, really screams
S – warmer crunch, warmer lead, good all around.
oh yeah, look into some ESP models too, specifically the SC500, and MH301 – those would be kind of a nice in-between for the RG and S. The ibanezes are cool, but so are the ESP’s you might want to check those out. They crunch like hell.