Derby's - just dreadful, might as well use a cheese grater. Razor burn and weepers every time.
Just shaved with a Derby today. It made my face baby-smooth with minimal irritaton. YMMV.
Nickshaves just did a review and it was impossible for him to get a close shave without major razor burn.The worst blade I have ever tried is the Dorco st-300. I tried them in my first wetshaving year(2009) in a fatboy.
I did a revisit about a month ago. Still the worst blade for me (in a 34hd,futur and r41)
For me, it's Wilkinson Sword. YMMV.
Worst for me are:
Derby Extras
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Dorco 300's
Merkurs
Dorco and Merkurs are so incredibly bad from my experience. I can shave with a Derby in a slant, but they're simply not sharp enough to be comfortable. Lots of tugging for me.
I have found that as my technique improves, my choice in blades changes. To me, the Walmart Wilkinson's deliver very smooth shaves, especially in a Gillette Red Tip. Put one in an adjustable razor and they are mediocre at best. I have yet to find a razor that gives a great shave with the Derby, but they are all OK. I haven't shaved with a Merkur since I bought my HD 3 years ago. Thought it was terrible then, but I was just starting to learn DE technique. Merkur would have to be my choice at this point as the worst blade, however I am tempted to try them again now that I have gained some experience.
Jeff