I can not give you a link, just my on practical experience.
I ran my Eizo L565 using the analog VGA connector on a GF3Ti200. I switched 4 weeks ago to DVI using a GF4Ti4200.
In my case the handling of the TFT became a bit easier, because no more adjustments have to be done for any screen resolution (using the autoadjust button), the screen handles now everything completely automatic. But that was it. I could not see any improvement to the visual quality, it is crisp and clear as it was before.
I once saw a post in another hardware forum, where the author said, that you could see differences if the analog signal or analog to digital unit was of low quality. Both was not the case for my old Asus/Eizo combination, so that is probably why there was not big difference, when going to DVI. Nevertheless I would always only buy a TFT with DVI connector, because this is the future and a quality feature.
However, moving away from my CRT to a high quality TFT was really worth the money. The improvements they have done to the TFTs in the last 3 years (mainly for the response times, viewing angles and colors) are significant. My wife is using a 3 year-old TFT, it is like day-to-night compared to my new one.
Cheers
Speedy