PSP's read and transfer speed? and 4gb hdd

Hello. Does anyone know how fast the psp can read the memorycards? Or does it depend on the speed of the memorycard you have?
I'm thinking of this 4GB hdd for psp compaired to this 2gb ultra 2 memorycard from sandisk ( f example )
Woud there be any latency when playing homebrews with this hdd compaired to this memorycard?

Please give me some info about this if you know something about it :)

The speed depends on what kind of memory stick you have. The HDD well go slower then the MS but well hold more. This is whare you choose, speed or size?