Before I got the 128GB microSD, I'd mainly used 32GB UHS-1 U1 card.
But the U1 cards are too slow for recording 4K video.
Sony A7R2 camera demands UHS-1 U3 cards to take 4K high resolution movie.
Higher writing speed reduce time to wait during continuous shooting.
I don't really shoot continuously so that I'd not had to have U3 cards.
A7R2 costs too much, not only the camera itself but fine lenses and many stuff.