either one will work.
never having used either one, other than obvious cosmetic differences, they seem have to have similar feature sets (and for that matter prices)
me personally, i chose a usb 2.0 enclosure that had a solid metal case, an very quiet fan (80 mm fan), and an external power brick as a power supply. i wanted a stable enviroment for a 250 gig HD that might be on for days.
i think having the transformer outside the enclosure should eliminate the additional heat it would otherwise generate within the enclosure. this might only be important if you plan on leaving the drive turned on f0r long periods of time, and you have something like a large harddrive that generates heat.
if you plan to use the enclosure for a dvd burner/recorder...or only for a portable HD that you don't use very often for long periods of time....i think it doesn't matter at all...