I was dismayed at the extreme slowness of my USB drive (Kingston Datatraveler) installation: it's been freezing up on literally everything. I had concluding that trying a USB installation was a bad idea.
But before I started to replace the normal (hard drive-type) installation with the liveUSB form in hopes that it would run faster, I enlarged the operating system's partition from 4 GB to 10 GB (all remaining space). This immediately alleviated most of the slowness; only Firefox still freezes up, and not as long. The distro (antiX) fit in 4 GB even after I installed extra software that made it much larger, but I guess it was still too little space.