Re: RG1570 or S5470 ?
The prices aren't as far apart in the US. Basically, though, you're paying for just a few more things.
1. The S has a thinner neck that needs titanium rods in it for reinforcement. Thinner doesn't mean better, though. It might be easier to go faster, but it'll be harder to play chords.
2. It'll have higher quality pickups. No need to replace these.
3. Obviously, you're paying for the flame or quilted maple top if it has one.
The RG gives you the Prestige treatment without the flare, it'll just be a good, solid, all-around player. The S gives you a little more if you want to be a shred master as it can make some styles a little harder to play on. (These comments are referring to these exact 2 models, not RG's vs S's in general)
One reason why I prefer an RG is the forearm cutaway. An S has never been as comfortable for me to play, especially standing up. I definitely recommend bringing a strap your next visit.