Personally I would not buy an RG350 just to emulate N64 or PS1, it is usually more beneficial to emulate the other older consoles.
I think it's perfectly reasonable to expect the PS1 to emulate well on the RG350. The PS1 architecture is quite a bit more similar to today's architectures and all the controls needed are on the device. Plus it's powerful enough to play all the systems that came before, making it an excellent option for classic gaming on the go.
Unfortunately, we're unlikely to see Sega Saturn emulation anytime soon for a similar reason to the N64. The Saturn is more of a high-performance sprite scaling engine rather than proper 3D hardware. (But dang, did those 2D games look good!) Strangely, Dreamcast emulation may be more feasible.
A similar problem exists with the Atari Jaguar which has a similar architecture to the Sega Saturn. The upshot, however, is that developers didn't know anything about these newfangled multi-processor systems and generally programmed it like it was a Genesis. Many of the games never even initialized the 32-bit RISC processors, opting instead to use the 16 bit processor that was intended to boot the system and coordinate the RISC processors. (Atari didn't exactly help here, providing really poor support to developers.)
Unfortunately, Jaguar emulation is still pretty nascent. Interest in the Jaguar is pretty low to begin with and the community around it can be... interesting. If you've never met Gorf, CEO of selling home-brew copies of Gorf for the Jaguar (not kidding), you haven't lived!