Best route is select your best choice internal (bare) HD mechanism and also an external case for it and put it together yourself. That way you know exactly what's in the case and can open it to swap drives around if you wish without voiding any warranties. Most drives from third party assemblers (LaCie, et al) that come completely assembled tend to use cheaper drive mechanisms and you have no idea what's in there without opening the case to see, which voids the warranty.
If it doesn't have to be small and you don't mind a power brick for power, go to OWC and get an OWC Mercury Elite AL enclosure for 3.5" drive with quad interface (eSata, FW800, FW400, USB2) and go to Frys online for a Seagate 1 TB Barracuda internal drive on sale for $180. You'll be into the whole thing for $280 or so and will have a rock solid, powerful, huge drive with 5 year warranty.
If you want the portability of a 2.5 drive, then get an OWC Mercury On THe Go case for SATA drives and a Hitachi or Seagate SATA drive. 7200 for performance or 5400 for energy savings. The Mercury OTG case is powered entirely by the FW cable, so no power brick to tend with. NICE!
Another variation is to upgrade the drive in your MacBook . I put in a 250 GB Hitachi TravelStar 5400 RPM and took out the 120 GB drive that came with the MacBook and put it in an OWC Mercury On The Go external case for 2.5" SATA. Love it. Hitachi is the current performance leader in 2.5" drives. In 3.5" I would stick with Seagate and Hitachi mechanisms.