Love the thread, Steve.
Maybe I'm looking at the blade vs razor analysis too seriously, but ....
There's an important variable that you might want to consider for you regression analysis ... I'll call it coarseness/thickness of facial hair. (Someone may have a better descriptor.)
Here's a generality that I suspect most folks would agree to: Having coarse facial hair would likely limit blade choice to the
relatively sharper blades. Having fairly fine hair would likely open up the world of blade choice. I'm not convinced that the razor is that significant of a factor here ... though I could be wrong ... as some of the more aggressive razors certainly can accommodate some
relatively less sharp blades (I've seen it in my Merkur Slant).
Now, I've got relatively coarse facial hair. If the blade cuts without pulling and tugging in my razors ... then it's a viable option, but I'll still weed out my preferences using the comfort variable. I suspect comfort is entirely YMMV as long as the blade is sharp enough not to pull and tug. There may be patterns within these subsets though.
Unfortunately in an EJ DE89, I personally would probably never use a Derby. That's more a reflection of the coarseness of my beard and Derby's ability to tug and pull my beard into submission, not the razor. This would probably hold true for most razors except for the most aggressive ... maybe I'll try a Derby in my slant someday

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It's getting late ... I'm starting to ramble!
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