Usually ability score.
It's just too hard to pass up that boost to Might, or Balance, or Endurance when those are prime, or Cunning, or Will or Grace. Hard to beat over the long haul. I like it in the D&D knockoffs where they're forced to use synonyms for the main attributes hehe.
I also liked it in the older 3e renditions where the feats were separated out from the abilities rather than an either or. I guess it just depends how many feats are ultimately on offer, but with only 6 attributes and especially if you're locked into those at char creation, or with just a few 1up mushrooms after you start, that always seems to be where I'm running.
But yeah, it's not as fun for characterization as the feats are. 5e is kind of wonky like that.
