it varies. All of those can be really interesting to watch.
I find boxing or wrestling to be the least interesting. Not a lot of boxing fights catch my interest now unless they are big names, or old legendary fights. Too much of nothing happening too often with boxers... Wrestling matches, I tend not to like because of all of the rules, and stopping that tends to happen during matches.
I prefer watching kickboxing fights, jiu jitsu matches, and MMA. Of coarse big names are most preferred usually, as they often come to fight and win. I enjoy it because of the display of skill, technique, heart, and impact. To see a lot of techniques be pulled off is really interesting to me.
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Don't you mind people grinnin' in your face