Once upon a time, BSN (Before Silk Naturals), I purchased a couple of kits from the-famous-mineral-makeup-brand-that-shall-not-be-named and in one was a very nice eyeshadow brush, just "full tapered shadow brush" is the name printed on the handle. BSN, You-Know-Who was my only MMU use, but the brush seemed to work well with its loose shadows.
Whenever I get new eyeshadow (pressed, not loose), I sit down with it, swatch it, play with it, and try to figure out which brush works best with it. Brushes are way different (weirdly) and it can make a big difference in terms of finish, color payoff, ease of application, and pretty much everything. With loose, this brush always works well. It and a scratchy Walmart cheapie are my only brushes specifically for all-over lid mineral shadow application, and I've never felt the need to look for another (needless to say, I never use the Walmart one - I should toss it).
Having said aaall of this, I am NOT advocating you buy the other brush. I would not advise you to spend the price of a nice order from Karen on a single brush! Plus I prefer to give support to small companies like SN instead of corporations. I find it easiest to work with the flat-headed brushes, therefore I would recommend the Ultimate Wet/Dry Eye Shadow Foiling Brush here on the SN website. It looks much like what I have and in fact I would like to replace mine with it. If you don't mind working with a round brush, there's also the Ultimate Eye Shadow Brush. I have a couple of the brushes from SN and they are wonderful. It's a little more than e.l.f., but completely worth it, and synthetic, too! No animals. (Not vegan, but natural brushes are unnecessary.) Give them a try and I can pretty much guarantee you'll love them.
I always post long replies. Sorry. But hopefully it's slightly helpful.
It was definitely helpful! Thanks for the thoughtful response. I have the "unmentionable" brush and while it did a good job, it is scratchy (like hard bristles on my eyelids) so I don't use it anymore. However, since you have had experience with that brush, and instead recommend the Wet/Dry Shadow brush, I will check it out as an option to my current lid brush!