CompactFlash is better for the empeg than SD, as discussed in some other threads on this BBS.

Reason: CompactFlash drives are IDE drives (technically they have a PATA interface), and they talk directly to IDE PATA controllers (like the one in the empeg) without having to go through any kind of translation. So a CF-to-IDE adapter does not have any complex conversion firmware which could potentially have bugs. Whereas an SD-to-IDE adapter would require a layer of firmware between the SD card and the IDE controller, potentially having bugs and compatibility issues.

I don't know if anyone has had success with an SD-to-IDE adapter yet, whereas more than one person has had success with a CF-to-IDE adapter.