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 had the luck of having 3 of my GPU's being Micron and surprisingly, they were all capable of being modded, in fact I had more trouble modding one of my samsung GPUs (which came OC by the manufacturer). The majority of Micron GPus that I have work just as intended. I only have a trouble with one of my Micron GPUs pulliing around 24-28 Mh/s , there's no work around for it - i've tried everything so I just have to deal with it. None the less I don't see Micron to be that bad.
RX 580 in case you are wondering.