Taking an average Aikido student who attends 2 to 3 classes a week and comparing them to a UFC fighter who trains 6 days a week and is probably in the 1% of their class (assuming they beat out a lot of compitition to get where they are) is to me like comparing your average soldier with a Navy Seal.
I'm not too familiar with the UFC but I have watched them in the past, but I think they, like many martial arts focus on technique and physical strength. There's a componant to Aikido that you may be forgetting....Ki.
I just read where an Aikido Sensei in Canada who weighs about 160 lbs, let a student try to pick him up while he was just standing. The student was I believe over 200 lbs and worked out, yet he was unable to life the 160 pound person.
Or the three students pushing against the Jo O Sensi was holding while at the same time another student behind him trying to pull him back. All four of these students were unable to move O Sensei. There's more to Aikido than technique and physical strength.
Energy and training to keep ones ego in control. From what I've seen of the UFC, ego isn't controlled...it's fed.