As measured by turnover at the top 10. Looking at the top 10 (Champ+1 through 9) annual HW's from Ring magazine over the last 5 years, there have only been 16 top 10 boxing HW's for 2009-2013. For MMA, Sherdog's December rankings for 2009 through 2013 have a total of 17 distinct names, about the same. (I didn't see any truly apples-to-apples annual mma rankings, but the results seems right). Since there's way more money at the top in HW boxing, why hasn't there been more competition as well? iI seems like the divisions everyone agrees are more competitive have a lot more turnover. Maybe it's just really, really hard to get guys to fight big guys--even if they themselves are big--because fighting big guys is just plain terrifying for everyone.