Not sure about the very latest TT, but TT and ATI both used the same video renderer, so the image quality would be identical.
The ATI player provides excellent picture quality, but people often have problems with it giving full DD/DTS pass through. The best I ever got was DPL via the spdiff in my set-up IIRC.
I found that if you're going to use Zoomplayer with the ATI video and another players audio, then install the ATI player, but *don't* run it. It can interfere permanently with the sound output, and I think I had to reinstall from scratch to get the audio to work with anything else.
WinDVD version 2.8 is not bad, and it gives its best picture using hardware motion compensation. Later versions don't seem to have quite as good picture quality (except maybe the very latest version which I haven't seen), but the sound seems to be better.
If you use Zoom player, then install the ATI player (don't run), then install WinDVD (for example) then install Zoomplayer.
Register the DVD filters selecting CinePlayer V4 and WinDVD audio for default wavout device, and you should be all set.
ZP even allows you to run random trailers before it plays the DVD in the drive.