How would an XL H1 SDI through AJA IO HD to the Apple ProRes422 codec (which is imbedded in the IO) compare to simply shooting HDV and transferring to a codec such as DVC Pro?
Sure, the SDI to ProRes codec won't compete with other SDI workflows but the Pro Res can be handled on standard drives. Pros and cons? Or is the ProRes more of an off-line codec solution? Sorry, I don't have the necessary technology set up, or I'd shoot a test.

ProRes is a better editing codec than DVCPRO HD. It's full-raster HD, which means it will retain the full luminance HDV when transcoded to, rather than subsampling to 960x720 (for 720p DVCPRO) or 1280 x 1080. (1080i 60hz DVCPRO)

Basically, the codec is cleaner and does less damage to the image than DVCPRO HD (given that the material has already been heavily compressed with HDV). Remember, DVCPRO HD originated as a camera and deck codec and is fairly long in the tooth by today's standards--not necessarily ideal for editing, whereas ProRes was conceived with the primary purpose of simplifying post workflows/editing.

A nice benefit of working in ProRes is that it's a square pixel format, which makes it easier to integrate graphics and have everything look proper in the end. I recently downloaded an update to my KonaLH card which now integrates the ProRes codec into the card, much like the I/O HD, and I can tell you that it's a nice format to work in, especially with hardware support.

There is no actual quality gain from capturing HDV as ProRes. What you DO gain is less heavy compression when further manipulating images in post production.

Just to make sure I don't have my wires crossed on this, Barlow: Can I capture (while shooting) from the Camera's SDI through IO and into ProRes? If so, then we would have better quality quality since we're bypassing the HDV codec and color space???
Kinda like a Wafian setup but using the more manageable file sizes of ProRes???

Just to make sure I don't have my wires crossed on this, Barlow: Can I capture (while shooting) from the Camera's SDI through IO and into ProRes? If so, then we would have better quality quality since we're bypassing the HDV codec and color space???
Kinda like a Wafian setup but using the more manageable file sizes of ProRes???

Yes, you can capture via IO, and you do indeed gain some quality, but mostly from a post production perspective. The actual perceptual difference (to the human eye) between ProRes, CineForm etc. and HDV is fairly negligible. The milder compression and added color sampling can make a difference in post production however, which will give you added latitude to really push the image before compression artifacting might become an issue.

AFIK, ProRes and Wafian (CineForm) are fairly similar in file size.

Excellent, that's how I read it but I've misread specs or claims often enough to know better than to assume...
Much appreciated.