1. "smudge factor" - does this ink dry quickly? 2. "dropped pen on point from distance" - is the pen resilient when dropped on/close its point? 3. "consistency factor over time"- does the pen deliver flow throughout its lifetime?
For #1, the experience is immediately soured if the pen is lifted onto my hand seconds after writing. Some brands have this problem - and it sucks. Ex: if writing quickly in a pocket moleskine, close it, and then open to find lifting on the other page.
For #2, most pens dropped on their head distorts the roller ball action. I've lost a few pens to this problem.
#3 some pens I've had in this list will not last the whole way through - either the ball rolls too much ink, or jams over the lifetime, rendering the remaining experience less than ideal.
I've been journaling for a few years, daily, and always carried a roller pen of various brands. My go to continues to be the uniball vision, which is good, but still is subjected to all above.