Neither. I wouldn't be too trusting on low-end double locking tremolos. If you want a Gio, either:
1. Get one with a hardtail bridge,
2. Get one with a non-locking Fender strat style bridge and hardtail it. Costs at most $10 for the hardtailing process.
If you want a double-locking tremolo for all those whammy stuff, go at least mid-end. Save up more.
Now my vote would go for the S series, but it's personal preference on my side because I don't really like the RG body very much (for me it's too sharp). But for you, best is that you try them both out and decide which one suits you better. Advantages of the S series are that they're much more lightweight and more compact, and the ZR tremolo is supposedly smoother.
i do agree with you man, the s is the way to go. solid feel from a thin body. but the bad thing is, once you've played an ibanez its just that damn hard to stop gettin them.