Please let us know the results of your tests.

Interestingly enough, the files as captured from the camera take up a lot more space than they should. A finished feature film (86 minutes) in ProRes occupies about 17 gigs of hard drive space, yet a 50 minute tape captured from the V1U camera in ProRes eats up over 30 gigs... which makes me wonder if there are actually TWO files being captured and one is invisible since the capture tape playback ends long before the "processing" of the frames is over (which runs about double, while lagging behind the camera at about 60%).

Question is where do these invisible files reside and how do you get rid of them after the frame processing is done?

Actually on my test I get roughly 40 Gigs for 45 minutes, but I am testing both HQ and Standard. Is'nt ProRes via compressor a different flavor - more heavily compressed maybe, and thats where you get the 17 Gigs?
I did not notice much difference between them, which I expected capturing from HDV. On a regular HDV clip, I had used some very heavy noise and film grain effects, so I added these to the same clip recaptured in standard ProRes. The ProRes clip looked better with the same grain filters - to my eyes, especially in movement and pans.
The render time is faster in the ProRes - not a huge difference.

I wonder if its testing this: recompressing 1080i60 into ProRes via media manager - then check the files size?