I did some more speed tests on various SD cards and USB flash drives I had lying around. These aren't extensive benchmarks, I don't really have the patience (or interest) to devote much more effort to this than I already have. These were just quick "hdparm - t" tests and then I dumped the output to a text file. I did each test 3 times and took the average. [table id=2 /]
Overall the Microcenter products did better than I would have expected. I was surprised how poorly my Sandisk ExtremePro UHS-1 SD card did but I suspect that is more an issue of compatibility of the newer standards with the EeePC card reader than the actual card. I was also surprised to see that, in general, USB flash drives outperform SD cards. If the Raspberry Pi results are similar then I think it will definitely pay to put the swap space and any other disk intensive things on a USB flash drive rather than the SD card.