Re: why the DC version is better, it's basically b/c it's the closest port of the arcade version. I'm not as knowledgeable of all the technical lingo, but I recall when the game released, all the 2-D fighting junkies talked about how this would be one of the truest translations from the arcades because the DC graphics engine is essentially similar to what Capcom used to bring the game to arcades.
It also explains why the DC got SO many games from Capcom when other publishers had already jumped ship. If you look at the list, it's pretty impressive; some include Power Stone 1 and 2, Project Justice, Tech Romancer, Canon Spike, and Third Strike. You'll see a few of these still have never come out on any of the other consoles (and others *finally* came out only recently). Capcom's ability to port to DC was fairly inexpensive.
So, in other words, the DC version is the truest translation.