It may give marginally better performance, but nothing big. In any case, it is debateable whether high-speed cards are worth the expense. My class 6 card has 5.3MB/s write performance, while a not particularily specified 1GB Transcend from a bargain bin still manages about 3MB/s.

If any, it is a waste to bother with expensive "high speed" cards that lack a specified sustained rate - pre SDHC "fast" cards are often tuned towards photo applications, and can write chunks of the size of an image at the advertised rate (which often is considerably higher than the 6MB/s of the top SDHC spec), but deliver average or even worse performance (with noticeable stalls) once you exceed their internal cache size. If they stall when getting beyond their cache, you'd better not use them for the swap file, or the performance of the whole IT will get abysmal.

Sevo