If for gaming purposes, an original (mark 1) SC-55 would be best suitable.
Although the SC-55 MkII has 28-voice polyphony (the original SC-55 has 24-voice), still a few games will sound wrong on the MkII.
Some music will have notes cut-off despite the increased polyphony. This has to do with the way some of the voices in the MkII are built-up. Where in the original some voices have just one layer, in the MkII they consist of 2 or sometimes more layers, effectively taking up more voices for one note.
The other problem you sometimes have is the -NO INSTRUMENT- on mainly the drum channel (10) with some games. Don't really know why this sometimes is the case since all the drumkits are available in either version.
Quality-wise it's better though, and it has 354 voices instead of 317.
MIDI comparison website: << Wavetable.nl >>
(Always) looking for: Any Wavetable daughterboard, MIDI Module (GM/GS/XG)