There were a number of reasons for me switching.
I found the fan noise on the VS700R starting to annoy me. The better control panel software for the Octa-Capture; when I had both connected I was finding that I tended to plug into the Octa-Capture just because I could use the auto sen function to get levels easily. I couldn't tell the difference between the pre's on both units; they both sound great. Finally, didn't need the extra inputs as I thought I would.
Besides, if it's good enough for Brandon and Seth, it's good enough for me!
Cheers,
jayson