Go with Sandisk, they're usually faster than the Sony's and cost less. I don't know about online, but from what I read they sell a lot of stuff under the Sony name that's simply dodgy. If it sounds too good to be true, it usually is. Respectable webshops are usually better in that aspect. If you go cheap on ebay chances are you'll be getting some terribly slow card.
Moving: General console discussion, not directly emulation related. Also, you're most likely to get more replies in the general gaming/console discussion