Okay, so I'm not really "testing", just having some fun.
I had a roll of 35mm HP5 in the camera and decided to take a few pics of a whiffleball player in my back yard (not my kid, but he's a handsome buck). I had already exposed half of the roll at iso400 and it was really bright outside, so I wasn't expecting great results on a cloudless day at 1PM.
I quickly finished the roll and remembered the advice from "way beyond monochrome" about exposing film, and decided to give it a try. So I grabbed a roll of FP4 and set the iso to 80. I developed the HP5 normally and developed the FP4 at normal time minus 15%.
I used Xtol stock for each roll of film, and wet printed on Ilford MGIV with no dodging or burning. The contrast filter and exposure settings on the enlarger were the same for each print. This paper has a little tooth to it so some of the sharpness is lost on these scans, but on the prints things look sharp where they should.
The results are below:
They both look decent on paper but I bet you can tell which is which. It was a fun experiment.