Greetings
I like Black Beauties, I find them reasonably sharp, certainly not as sharp as many stainless coated blades but what I do find is that they are ultra face friendly and a forgiving blade, I have used very many of them and find they do very well in more aggressive razors and do not perform too good at all in really mild razors. I only use them once and bin them which for me is not an issue as I shave only infrequently with DE razors and as stated they are cheap anyway.
Treet Durasharp blades are a different animal altogether and very unusual in that they are carbon and PTFE coated all over including the cutting edge, whereas Treet Black Beauties just have the black 'coating' on the blade only not the cutting edge, I find the Durasharps a little sharper and they last longer I use them twice although I am sure some people could get more good shaves from them.
I think many people hate the Black Beauties because they give a very different face feel, the terms tug and drag are too extreme but they do feel more like (but to a lesser extent) a shave with a wedge blade or a straight razor or an old carbon SE blade designed to be stropped.
Regards
Dick.