Recently I had the misfortune of having a debian update screw up my docker daemon and I ran over to Best Buy to grab any-old-USB drive to use as a new OS drive. As it happens the SD copy over went fine, but as I performed basic "setting the server up" operations like copying over the old data (50 GB of various sizes) and firing up docker-compose scripts, performance deteriorated rapidly to the point where a docker install of a lighttpd container took at least 30 minutes and the system became effectively unusable.
The poor-performing drive was the PNY Elite-X Fit, USB 3.0, 128GB, purchased for ~$22
I've switched back to a SanDisk SD card for the moment which is perfectly adequate for the next few months but I hope to get back to running off a USB soon when I'm not so busy.
For the Pi 4, a faster USB drive (e.g. SSD or NVMe in adapter) will be a massive improvement for many things (though some operations like launching a browser won't be vastly improved).