USB 2.0 data transfer speed = 60 megabytes per second.
PCMCIA data transfer speed = 75 megabytes per minute.

PCMCIA external drives are suitable for data backup only

Those data transfer speeds are theoretical maximums also. In actual operation, you’d seldom if ever reach those rates. Drive rotational speed plays a big role in just how much data you actually transfer, so when you are choosing a drive you should be attentive to that factor. Faster spinning drives, of course, are more expensive than slower ones.