The only one anyone pays attention to is a fighter's record. Crystal Hudson of MMA Madness believes this should change and argues variables such as submission attempts, striking accuracy, and successful guard passing and takedowns (or defended takedowns) could be useful in evaluating fighters and their performances:
The data described above can be particularly instructive when previewing a particular match up. It will allow for a direct comparison of skill sets as a basis for any pre-fight assessments. With more meaningful discussion possible, one hopes there will be less reliance on generalizations of the "world-class jiu-jitsu" variety.
Fight statistics could also be useful in illuminating controversial decisions. It might help observers to pick out the factors that may have most influenced the judges. At the very least, the data will provide a useful talking point in the endless rounds of debate that follow such decisions.
Lastly, performance data can provide a useful counter balance to purely subjective rankings. Most outlets that publish rankings will readily tell you that their methodologies consist of asking a group of people for their opinions as to who is a "top ten" fighter. Hard data will help push the needle on the opinion spectrum more towards the objective. Taken together, rankings and statistics can be used to create a more complete picture of each fighter.
All true, I just think you have to really narrow the subset of what you're measuring. Guard passing by itself doesn't tell you much, particularly considering some BJJ players will allow their guards to get past to set up chokes, sweeps or reversals. Instead, perhaps successful guard passing against black belts or Mundial and Abu Dhabi-level competitors might be more useful than merely tallying how many times X fighter passes someone's guard.
Of course, that breeds the other problem: percentages versus tallying totals. It will difficult in the early going figuring out which demarcations are informative. When baseball players successful hit the ball 3 out of 10 times on average, that's considered a good performance. Well, how many times does one need to pass guards or land takedowns before they've crossed a meaningful threshold?
Employing and discovering useful stats in this sport will be difficult. I venture to say when the mainstream really sinks their teeth into MMA, we'll see outlets like ESPN - with teams of researchers - begin to develop some sort of system.
Until then, ambiguity is the name of the game.