It does matter. Bigger buffer=faster performance. If it's not too much more, go for a drive with 16mb cache. Also, if possible, wait until March or so to buy a hard drive. Floods in Thailand have caused hard drive prices to go through the roof. Wait a bit for reconstruction and prices will drop again. I bought a 750gb 7200rpm 16mb cache 2.5" drive for $100 pre-flood. Now, that same drive costs well over $200.