As far a pure badger, I would say it comes down to construction. The only quality eaxamples I have found are simpsons and shavemac. Others seem to have really poor badger hair and/or the sizing of the knot/loft is all wrong. Pure badger, as in courser "low grade" hair can be done well though.
When it comes to the traditional US made shaving brushes I have never come across an example of a badger brush labeled other than as "Pure Badger" or "Imported Badger". And the examples I've found have varied in quality from very good to as nice as anything found in any modern brush. In my traditional English made brushes there seemed to be three major grades; "Pure", "Best" and "Super". I've heard some were labeled as Silvertip (Kent in particular) but so far I have not come across an example that is not a brush made in the last quarter century or so.
Here's a brush my son bought for me a while back. Not sure if it's "pure" or "black", but it is without a doubt, my floppiest, scritchiest brush that I own. And I LOVE it.
I look at it like this: Best is sorta the three band version of two band Finest, in terms of face feel. But comparing one to the other in broad terms, or even from brand to brand, is nearly impossible. I have a couple of Bests that the hair is as soft as most 3 band silvertips, and some that are scrubbers. I have some inexpensive chem treated tipped Finest that are gel tipped softies, and high end Finest that give a heck of a scrub. I enjoy a silvertip mixed into the rotation, but generally prefer Best and Finest for the backbone. I think Pure gets a bad rap because of all the stupid cheap Escali and Tweezerman type badgers that sell for ten bucks, and are tied with a total of seventeen of the worst hairs they could sweep up off the floor. IMO, these brushes are the biggest reason that people say they have tried badger and that it sucks. Pure has way less backbone, and is pricklier. But a good dense one is a really enjoyable experience. Here is a $90 pure laid down next to a $45 Finest with a similar sized knot. The Pure has a lot more hair. Totally different feel of course, but a great brush. My point is that regardless of the type of hair, the more there is, the more you pay.
Thanks, Andrew. I should have added this: Both of these brushes are within a mm of each other where they exit the handle, but have the exact same effective loft over the glue bump. So why does the stiffer Finest have twice the bloom of the floppy Pure that has seen ten times the use? The only answer I can come up with is density, and possibly how tightly the knot is bound.
Here's a Shavemac pure (I have 2 pure knots from Shavemac). I've had a few best knots they can be very good to quite scritchy. The Shavemac is what I would call slightly scritchy and from my experience consistently. Paint brush type strokes I don't notice scritchiness.
My first brush was a Pure badger and I thought it was great until I tried a Best grade from a different company. Both had the same backbone but the Best grade was a lot kinder on the skin. One of these days I'll get around to trying a Super Silvertip but I'm happy with my Best for now.
My first brush was an Escali pure badger. $10 on Amazon. I wasn't sure that I was going to like wet shaving and didn't want to spend a lot to find out. I knew after my first wet shave that it would not be my last, but I never saw any reason to upgrade my brush. I have changed everything else several times, but I still have that same brush. Maybe it's time I find out what I've been missing. I do have to say though, my experience with the cheap"pure badger" Escali had been positive. More than 3 years later it still works great.