Soundwise all pretty different. I believe:
1) Woods are different (3120 2020 are mahogany, and 2570 is basswood)
2) SZ is non-trem and set neck, so probably comparable in many ways to an LP.
3) Neck profiles are all different (SZ thickest and 2570 thinnest, though I could now be mistaken since they may have changed the profiles)
4) SZs use SD/IBZ pickups, 3120s have Dimarzio (TZ PAFPRO) and 2570s have Dimarzio/IBZ pickups all different models.
Depending on what kind of stuff (music) you're playing, I would go with the RG3120 first, as it at least has a floating trem for you to work with, rather than the Squier type trem. The SZ is second choice.
I may be biased because I have an 02 RG570EX and assume it is close to the 2570E (... edited ... I didn't mean that my guitar sucks. I love it (TZ/JB Jr/PAFPRO), though am currently playing my Les Paul copy a bit more now).
1) Woods are different (3120 2020 are mahogany, and 2570 is basswood)
2) SZ is non-trem and set neck, so probably comparable in many ways to an LP.
3) Neck profiles are all different (SZ thickest and 2570 thinnest, though I could now be mistaken since they may have changed the profiles)
4) SZs use SD/IBZ pickups, 3120s have Dimarzio (TZ PAFPRO) and 2570s have Dimarzio/IBZ pickups all different models.
Depending on what kind of stuff (music) you're playing, I would go with the RG3120 first, as it at least has a floating trem for you to work with, rather than the Squier type trem. The SZ is second choice.
I may be biased because I have an 02 RG570EX and assume it is close to the 2570E (... edited ... I didn't mean that my guitar sucks. I love it (TZ/JB Jr/PAFPRO), though am currently playing my Les Paul copy a bit more now).