Betting favorites or underdogs is probably the most misunderstood thing in sports betting.
On the one hand, you have people thinking that only betting big favorites such as dominant champs or one-sided match ups is a sure way to grind out a small but secure profit over the long term.
On the other hand, you have people who think you bet against everyone else and bet on the underdogs because anything can happen in MMA so therefore you should profit over the long by betting underdogs.
Both assumptions are wrong. Sometimes it makes sense to bet on favorites, sometimes it makes sense to bet on underdogs. If MMA betting were as easy as “bet only on -300 or bigger and you will profit” or “bet the underdog” bookies would go out of business.
There are definitely anomalies in the betting market you can take advantage of but they’re more subtle if the inefficiency is obvious it will quickly be corrected by bettors. Basically, betting markets work similar to financial markets. A simple betting strategy as the above simply doesn’t work. If you backtest any type of odds you will neither strategy yielded a profit.