I ain't had a problem sharpening any glue on BH.. Some don't seem to stay sharp though.. I've had them shaving one day and they seem to dull in the case..

My "go to" Bh is the Ace Std..

My favorite two blade is the STOS, but the Magnus and Zwickeys sharpen up just as good.

Lots of good heads out there, these are the only two blades I have experience with.