I'm with Bill. There are large differences in performance in other types of flash card, for instance compact flash in terms of speed etc. However Panasonic declare their read/write performance, and without having looked at the spec of other SD cards it would be logical that they would need to match a basic spec to gain a license to manufacture the format. Therefore the only difference to justify price differentials would appear to be the eventual reliability.

It is easy to see performance differences in digital cameras when saving large TIFF images to flash, which may be 9 MB each picture for instance, for technics and midi files any performance difference is likely to be insignificant.