Quantifying qualitative data in a useful and consistent way is tricky. Professionally, I don't Likert (see what I did there? ). In fact, I have a t-shirt I wear to professional conferences which says: "Statisticians: They Don't Likert". I am the hit of the party. However, I wish you luck in that endeavour.

In any event, when I have a great edge usually what happens for me during the shave is that there's a smooth glide through the stubble and (on the first N to S pass) there is very little stubble left. Not quite BBS, but very close.

A good but not great edge isn't quite as smooth in its movement, and leaves more work for the S to N (second) pass to clean up. I don't mean there is noticeable stubble after the first pass (I could get away with going to work off the first pass, for example) but there is a rougher feel.

James.