Offline CPU for sim, Online for competitive
I will die on this hill, the CPU is fights significantly more realistic than 99% of players you'll face online. UFC 6's (and 5 & 4) are criminally underrated and I haven't seen anyone give it the praise it deserves. If you're looking for a realistic experience with realistic pacing and ebb and flow, the CPU is your perfect dance partner. Of course difficulty settings make a difference, but I think Pro is the sweet spot. My guess is that Legendary difficulty will more or less force players to be more formulaic & actively looking for exploits to best the CPU. On Pro you can pretty much be dynamic and just fight realistically to the best of your abilities with great results.
Online, just watching the more popular people like NazUFC is just a whole new world. I wouldn't even call it "arcade" per se, I mean, I guess it is, but at the highest levels, from what I've seen, the experience is anything but realistic. Every single player is "combo-minded." Every offensive move consist of three-strike combinations. The strategy is formulaic. Learn the "best" combos, understand the best moments to unleash them, rinse repeat. I just watched NazUFC beat the supposed #1 ranked UFC 6 player. NazUFC was more methodical, took his time, activated his flow state and knocked the guy out after an extended combo that essentially stun locked his opponent in place. This isn't real fighting. There was no precision timing or a perfectly placed shot. No opening created by feinting, no perfect anticipation of your opponent's movement to land that perfect strike. It was just having a solid grip on the mechanics and utilizing features like flow state at the most opportune moment.
In contrast, fighting against the CPU affords players to fight realistically, relying on spacing, baiting the CPU to make mistakes, and capitalizing on those mistakes. You can throw combinations, sure, but it's not a combo-based strategy. You pick and choose your spots, one shot at a time, rarely ever extending your combos past two strikes. KO's come swiftly after a single perfectly timed shot.
Anyway, not a complaint, just stating the facts. I love UFC 6 and the games that came before it, but against the CPU. I'm not looking for the toughest challenge, but the most realistic experience, which can be found only against the CPU.
