I would guess revenue, as sales numbers really aren’t that relevant anymore. That’s another thing I forgot to bring up in my previous post - that the crazy focus on pure sales numbers, rather than earnings, has become even less relevant as we now have flexible pricing.
If you must quantify a track’s worth, earnings would be the logical choice. Not sales numbers on a $0.01 track. 
Most other big stock sites stopped displaying sales numbers and earnings years ago. It really doesn’t do much other than inspire copycats and hackers, boost egos, concentrate sales to a few select tracks (buyer group mentality), and scare buyers away from 0 sale tracks.
Of course, this is most likely not that good for mega sellers.