When I'm researching pjs and players I always find reports of first-hand experiences useful so I thought I'd offer my own small attempt. This is not extensive, and is highly subjective .. being mostly qualitative rather than quantitative

.. but hopefully it may be helpful to someone.
I used a Sanyo Z2 with a Draper Onyx 92" 16:9 fixed-frame screen, gain 1.2, in Eco mode. The projector was left uncalibrated for all tests. My main interest was experimenting with various DVI inputs, but as a base-line I chose to use one analog which I expected to prove of lesser quality than the digital variations.
I used only one DVD, Fellowship of the Ring EE Region 1. I did compare the region 1 and region 2 versions in one test but there was barely any difference, and since the DVD players I have are both primarily NTSC players the region 1 was what I used throughout.
Component:
To sample this I used a Sony 730, progressive into component input. The first thing to say about the 730 is that it's dark, very dark. Others have commented that something seems wrong with the gamma of this machine and it needs the pj cranking up to bring it in line with my other DVD players and also the HCPC.
Once that's done the picture proved satisfactory and certainly hugely better than non-progressive. Colours are good, and only a little judder was present on the large pans over Hobbiton. Without any other reference point I did think there was a little graininess .. indeed, after looking at the DVI sequences I can definitely say the main difference is this aspect.
If this was the only source I had I'd probably be perfectly happy with it and not know what improvements may be possible.
DVI:
My first test was with a newly-acquired Momitsu driving at 720P. The picture was stunning. Gamma was fine without fiddling, colours full and rich and the picture smooth, pans were no better so clearly the juddering is due to pulldown or other mechanisms about which I understand little.
Next I used my HCPC which has been my main player throught the Z2's short life. First I used PowerDVD and abandoned it early into the test. It was grainier than the 730's component feed and was very poor compared to the Momitsu.
I then used TheaterTek and of course this is a great improvment. However, it has to be said IMHO it was no better than the Momitsu, in fact in a couple of places the Momitsu seemed to produce a clearer picture .. in the long shot of Sauron's demise in the Prolog in particular, the Momitsu revealed more long-distance detail than TheaterTek, not by much definitely more texture was present on the far rock faces etc.
Now, it could be gamma again, I don't believe it to be Black level though clearly only an Avia-based calibration will sort that out, I have problems calibrating gamma, but whatever it is there was a difference. I fiddled with TheaterTek's Gamma setting and could resolve the difference with that alone.
Finally I tried my newly-installed X-Card into D-Scaler. My battles with this are well documented in the Sweetspot thread, suffice to say here that the picture quality lags both TheaterTek and the Momitsu .. strange because the Momitsu has a REALMagic chip in it like the X-Card. It's still better than the analog, it'd be interesting to feed analog into it and then display that perhaps, but that's not what I got the card for.
So, what's my conclusion? The obvious thing is that DVI r00lz.

Second, a cheap player like the Momitsu, and probably the Bravo too, is clearly a match for the best HCPC-based DVD player. Clearly I'd need to do a lot more testing, calibrating and fiddling to 'prove' the point, but I'm convinced that I lose nothing in PQ and gain a LOT in convenience in using a DVI-based DVD player compared to an HCPC.
Don't know if this ramble is useful, hopefully it will be to someone.