Fast CD ripping on old MacBook Pro, slow ripping on i5 PC?
Installed Mavericks on the same, slow ripping PC onto a USB external drive. After adjusting one or two kexts, I had a mostly functional OS X environment.

Updated and ran iTunes with the same settings. Ripping is now mostly at 20x on the same CD drive. Looks to be a limitation with iTunes for Windows, or Windows itself. Who knows!