The new MMSPlus is the best SMS emulator on the PSP, apart from one thing - whilst most games run perfectly, some seem to run too fast. Sonic 2 is a good example (the music is speeded up), but Sonic 1 runs normally - I've tried different versions of the game, but it still has the same problem. Changing the system from NTSC to PAL seems to sort out the speed issue, but the game then doesn't run as smoothly. Has anyone else encountered this? All the other SMS emulators (PSPMaster, e(mulator)) don't seem to have the same problem.
Oh, and the reason why I prefer to use MMSPlus is because of the Z80 overclocking feature, which reduces slowdown in games like Sonic 2 (the other emulators don't have this feature).