FW or USB? Upgrading to avoid disk slowdowns

[atothegreen]

I've had a persistent issue when I'm running sessions using my 003r with a G-Drive daisychained to it via a FW 400->800 cable, I occasionally get "DAE can't get audio from the disk fast enough" errors. Usually it's when I'm running sessions with more than 20 tracks (which is most of them), and only while bouncing, which is irritating.

When I run the same sessions using the drive directly into the FW 800 port on the side of my MBPro and an Mbox2, I don't have any issues of this sort, ever.

So, I'm considering an upgrade to the Mbox3 series and ditching the 003r, and since the Pro still only has a FW400 port and no 800, I'm thinking I should just go with the USB. I'm not concerned with losing inputs, since all this would be used for is single or dual-input tracking at the most. If all I'd lose is low-latency monitoring, I'm really not that concerned. Are there any other differences between the Pro/FW and USB models that I'm missing, other than the different numbers of inputs?

Please tell me if a) I'm nuts or b) there's a workaround for this issue. Would a hub make any difference? Am I doing something horrifically wrong?

2010 MBPro 2.53 GHz Core i5 processor with 8 GB RAM running Snow Leopard 10.6.8, PT LE 8.0.5 with 003r or Mbox2 USB, G-Drive 1TB external via FW800 or 400 through 003r