I checked out the flashlight forums posted above, and found an interesting thread between a couple of guys who say that they can (just barely) tell the difference between the 125 lumens vs. the 225 lumens with the Surefire M3 flashlight.
That's a difference of 100 lumens! Knowing that they can barely differentiate b/n a delta of 100 lumens makes me feel a lot less stupid about not being able to differentiate b/n a delta of 40 lumens (the 6P's 65 lumens vs. the 9P's 105 lumens)
Their discussion is at:
http://www.surefire.com/ubb/Forum9/HTML/000026.html
and a description of the SureFire M3 is at:
http://store.yahoo.com/botach/surfirm3mil9.html