This only way to achieve high external disk performance on a MacBook Pro is with eSATA by means of an eSATA card inserted into the ExpressCard/34 slot. I just advised a consulting client on this very topic, saving him the huge expense of buying a Mac Pro, allowing him to move his external eSATA enclosure from his PowerMac G5 to his new MacBook Pro.
While less expensive eSATA cards easily outperform sluggish Firewire 800, only the Tempo SATA Pro with its Marvell chipset offers the highest performance for a dual-drive RAID stripe as used in Optimizing Photoshop.
Apple’s ill-advised elimination of the ExpressCard/34 slot in the latest 13" and 15" MacBook Pro means you can’t use eSATA in those models (and nudges those models towards consumer-grade status, unsuitable for a desktop replacement). See my June 9 comments. Stick with the previous generation models (refurbished) or the current 17" model, all of which have the ExpressCard/34 slot.