FWIW, I have a Plextor M6e 256GB, a 941 128GB, and a 750 PCIe 400GB model (which I'm starting to regret - the form factor, not the drive). I got the Plextor because it was the only PCIe B+M card (2x2.0) I could find (Sandisk A110 being the other, quite old, warranty-less option) but unlike the other two, it's given me nothing but problems. Anecdotal, single sample, but there you go.
I needed B-key for my vPro NUC 5i5 (why, Intel, why) and if doing it all over again, I'd just go with a S3500 M.2 for reliability, especially if I were using it as a hyper visor boot drive -- and in fact, as I do use my NUCs, especially the vPro ones, as test or supplemental VM hosts, it's on my shopping list for exactly that purpose.