To me it comes down to skill. Sometimes it doesn't matter how big the guy is your fighting, if he can't fight and has no skill, then you should win. In the 2nd UFC, when the weight classes were open, they had a sumo wrestler fighting a kickboxer and the sumo guy got knocked out after 3 punches. I'm no MMA fighter and nor do I want to be one but I've been in fights with people bigger and smaller than me and sometimes you win and sometimes you lose. It comes down to skill and who wants it more.