Yep, purely my personal preference. The rankings are derived from repeated pairwise comparisons, or matches, between switches, after they've been randomly assigned to a set of keys. This is what I see when 'scoring a match' between two switches:

Scoring match (1 of 50): h vs '
  Choose an outcome (1="h" wins, 2="'" wins, 3=draw): 

When I see the prompt, I press each key a bunch of times and try to decide which wins or if it's draw.

It's probably also worth noting that I'm very new to the hobby, and I'm still trying to figure out what I like. I just happen to be somewhat data-savvy and thought this might help me understand my preferences.