The write-speed is important for certain types of shooting. If you shoot video or even a lot of high-speed continuous still shooting the write-speed will offer the best performance. I don't shoot video, but I do a lot of transfers from my SD cards to a portable hard drive and the cheap/slow cards take forever to transfer images.
I tend to shoot on only 32 and 64 GB cards. I actually like having all of my images in one place - on my camera. Not that I can't take care of a small wallet full of cards, but I know I take care of my camera and the card within. However, I back up my images every day to my My Passport Wireless hard drive, and the real keeper images I backup to the cloud if WiFi is available, or my 64GB phone if not. I find having my images only stored on different cards...makes me nervous.
Lately I've been using Sony cards and they've been great.
And, always carry a spare. People do report of bad cards now and then. Another reason to shoot, check your images, shoot, check your images, shoot...