Firewire Bus powered drives - any disadvantages?

[vexecuter]

Hey guys,

I'm eyeing up a firewire storage drive; either the Lacie Rugged 500gb 7200rpm or the OWC firewire bus powered 750gb drive (7200rpm).

I have noticed though that some firewire drives are mains powered. I'm using PT LE, with a good few tracks and virtual instruments and plug ins, on the go in different locations on a macbook pro. The mains version is great when I'm anchored to one place, but sometimes I'll need to do a couple of hour recording sessions without mains access.

My question is; what are the disadvantages to bus powered firewire drives? Is there any performance decrease, danger to data loss or other things I have missed out versus a mains powered firewire drive.

Many thanks,

V.