Samsung is the best
Micron is the worst.
It definitely matters, but not a ton. 1 or 2 Mh/s if you bios mod them correctly for ETH.
Samsung cards are way better for Cryptonite, at least in my experience.
I get 30.x with micron (sapphire nitro+ 8gb).
Hynix about 28-29.
Will buy some Samsung tomorrow.