I have oct gates on all my sticks. Makes it better for other things outside of SF. I like the old era of 8-bit gaming and even some of the re-makes, and games such as pac-man, play so much better on an oct gate, as appose to a square gate.
Spend time trying both and decide what you like. They're not all that expensive. I guess you could say, just keep the sq and turn it into a 4-way, but a true 4-way is too restrictive, so an 8way is the next best thing. Still play SF, and get that 4 way feel for all the other games out there, that play better on 4-way.