The 2550 is front routed and the 1570 is back routed + different pickups - otherwise the neck and the hardware are the same.
I've always preffered back routed guitars, esp guitars without pickup rings - they just look minimalistic and lean.
The two guitars also have different paint jobs, I believe. But you're better off getting a RG2xxx series guitar simply because it's a better bargain. I believe they only cost about US$100 more than the RG15xx series guitars.
The 2550 has the dimarzio pickups of the bat and a pickguard. The 1570 has ibanez pickups and is routed from the rear. But, if you wanted to get the 1570 and change the pickups to nicer dimarzios that would cost only a little more than buying the guitar with the lesser dimarzios and you could get evos or something else that's better sounding than the Ibz/dimarzio pickups. Also, you need to take into acount that because the 2550 is more expensive, they will have put more time into playing really well, having all the fretwork neater and more precise, and having all set up in the factory, like for example, what's going to make a Jem nicer than an RG? It has the same basic parts, a different neck profile mind you, but the same trem and tuners and nut and body except the monkey grip and claw, the biggest difference is that it costs a thousand dollars more than the nicest RG so they put more time into all the detail work. The monkey grip sure as hell isn't worth another thousand dollars, it probably takes a router 20 seconds to cut one out. It's the improved detailed work, such as fretwork and setup, that facilitate the thousand dollar price jump. damn capitalism.
It's hardly the improved fretwork and setup that makes the JEM cost so much more than the highest end RGs; it's the fact that it has Steve Vai's name on it. I'm not saying that they don't put a little more time and effort into the guitar, but it's certainly not a thousand dollars worth of effort.
Yeah my bad, I totally forgot to mention about his name. Also, I didn't mean that the extra attention to detail was actually worth that much, I meant that they charge a whole lot more for not nearly what it's worth in actuallity. I'm sorry I forgot to mention the name part, I was thinking about it and just didn't type it, now I feel really stupid. :^(
they have some of posts on vai's site about his name and the jems.it doesn't really have his name on it.i think he tried hard for the guitar not to be completely associated with him.it's not really a signiture or else it would say something like the vai signiture model,much like an ibanez js.
But that makes sense, for a guitar that has his DNA in it (in whatever minimal amount). And "JS Series" hardly says "Joe Satriani" any more than "JEM" says "Vai". They are associated whether or not the name is spelled out on the guitar itself.