Eh, I think most flash memory is made by a few companies and then packaged (as in, put on the circuit board, plastic case around it, put in a little cute carry case, and sold) by a myriad of companies.

If there'* a speed rating, like there is on ComactFlash, then go for fast, it'll help you get to your next picture faster.

For instance, I notice that my Olympus camera is a little faster when I use a xD card, rather than a SmartMedia. It'* a little faster design, and the pictures save quicker.

I got a really good deal on my xD through amazon.com. They often have sales too.