From my own personal experience, I think MMA is easier to predict than Football, so a gambler is likely to win more bets when such a gambler just focus on MMA betting, but the important thing is that, such a gambler must know MMA stars in and out, he or she must watch all their matches and know their strengths, weaknesses, capabilities and tactics, this is the only way predicting and winning most of the MMA betting would be very much easy for the gambler.
Football prediction on the other hand isn't something that is certain or very easy, this is because football is full of uncertainties, a small team from no where can get up and by luck, beat the bigger team every one is expecting to win the match, last year's world cup where Saudi Arabia beat Argentina, is a good example of what i am talking about.
Of course I would agree on that. MMA certainly is much easier to predict accurately. Its only mathematics if you consider the more variables you have to work with, the more your prediction starts becoming vague and out of focus.
MMA has the upper hand for the gamblers. Not that I believe it is possible to predict anything with 100% accuracy. I am sure however, that you could get a close enough number for whichever gambling strategy.
But you can get a slight edge in, a few extra percent maybe even a two digit number... It really depends on luck anyway. So both are unpredictable with MMA being less so.