The Capcom Classics Collection 2 version is emulation, but it's a terrible one with tons of sound breaking audio glitches, and noticeable input lag. In this day and age, I'd say either go with the PSX/Saturn Street Fighter Collection for Super and Super Turbo (though Super seems a bit easier, and Turbo's AI was toned down to be at the same level, whereas the arcade's difficulty is much, much higher than any of the other versions of SF2, as indicated by the Japanese title 'Super Street Fighter II X - Grand Master Challenge'), or I'd say just emulate the arcade version. The music is very close to the arcade, and the graphics made much better use of the Genesis' limited palette, which on Super just looked like they took the BGs and just simply lowered the color depth in an image editor and called it a day. In the end, I'd say the Genesis' version of Special Champion Edition is far superior to the Genesis port of Super.

That'd be the only real reason to play this version. The Genesis version has the 'Extra' mode though, which is unique to that version and faces you off against every fighter in the game. His legs only have 2 animation frames on the Genesis, but on the SNES version they have 3 frames:

One actual example of missing frames is Guile's standing animation (in both Genesis versions). Back then I was defending it, saying it surely sounds better on actual hardware, but it doesn't), and the graphics are much more detailed, and aren't missing any big details like the SNES versions of World Warrior and Champion Edition/Hyper Fighting. I used to be more upset about the censorship, and defended the Genesis version over the SNES one as a result, but these days I'd say I prefer the SNES version if I had to choose between the two, because the music is very close to the arcade's (I thought the sound would be better on an actual Genesis, but after I bought a copy a couple of years ago, I discovered it's just as bad as on emulators. Cammy's standing animation was actually butchered on the SNES version, as they tried to censor it because her chest was moving a bit. Ken's stance has the exact same number of frames. In the Genesis version it looks a bit choppy compared to the SNES version's smoothness.

All snes versions