Now we're speaking my language...
I have two Big Blues (one originally SSF2, the other originally Alpha 2), a Z-Back, an old candy cab, and a HS-1 all running Hyper Fighting. I actually ran the Hyper Fighting tournament at CAX last year (and use to be on the EVO staff ). SF2 was also the first pinball I purchased, so I love me some SF2.
Which is better? Super Turbo > Hyper Fighting > the rest of the "II" series. One of ST's major flaws is that the AI is ridiculous, so some people throw down 200-300 bucks for the board and then are miserable when they don't have anyone to play with and can't make it two characters versus the CPU. Never allow a friend to ST alone...
I haven't fired up GGPO in forever, but if I really wanted to play ST and couldn't get people together to play, I would go that route. I find it is way more difficult to find good matches on HDR XBL/PSN than regular ST on GGPO (unless things changed in the last 6 months). On HDR: you blow someone up and they ragequit/hate mail ASAP OR you find someone good that is building a streak, you break the streak and they disappear forever.