Genesis version is the one I played, but didn't know about the extra levels. It's just my go-to system. I've tried the SNES version but didn't like the audio in comparison so didn't play it for very long.
I actually haven't played much of Lost Vikings 2. The SNES version looks a lot better visually than the others, mostly because it mimics the first game. I'll have to play both versions of that one.