I agree that I've noticed if I shave the weak 5 o'clock shadow I get with a daily shave it is not a very good test of an edge. To that end, the only way to extrapolate data with any form of expedience for me, is to prepare a blade, wait for a bit of growth, then do a spot shave. My neck hair is thickest and mustache is most sensitive to tugging and pulling. I can extrapolate a little information from the cleft on either side of my chin (by how clean I can get that area), and my cheeks/sideburns really don't tell me much because the hair there almost seems to fall off with any sort of reasonably sharp edge. But if it DOES tug on the cheeks, the edge is a lost cause and the shave will bite all around.

At any rate, I'll shave an inch or 2 of an easy area, then the same amount of a problem area with the blade prepped one way. Then I'll wash up, change how the blade is prepped, and try again. This way I can test 2, 3, 4 things in a setting. Then if the razor is shaving well, finish up the easy stuff (cheeks, sideburns, etc.) - or switch to a good shaving razor if it isn't - and prep the blade for another set of tests in a few day's time.