I was referring to modern SATA standards.  Either at II or III speeds, I believe no CF card currently on the [consumer] market [*]can perform a comparably priced SD card.  But it's possible there are a few exceptions.  The $50 32gb 300MB/s SD card I got can outperform any other CF card currently on the market (there's a 64gb and 128gb model but they're prohibitively expensive).

But either way, I think my point still stands - any SD card that could max out any of those bus speeds (to switch back to IDE and old Powerbooks) is cheaper than a comparable CF card.

[Also, I've found that a $10 SD > CF adapter works perfectly in that respect - giving both the benefits of cost for the SD card and compatibility for the CF adapter (i.e. you use the CF adapter on the Powerbook, but the SD card adapted to that adapter - sorry if that's not clear).]

[* SSDs can outperform retail-market flash memory.]