It has been a few weeks, so I'll close the test. The results are pretty much as I expected... Everyone picked the TGMC clip as the better looking one, and I agree. TGMC is an excellent deinterlacer that creates a very crisp image. But, everyone pretty much agreed that, at least for this source, there wasn't a big difference between TDeint and TGMC, and under normal viewing conditions, no one's really gonna care.
So, what was the point of this test? Well, I've been encoding video for years, and I've seen the trend move slowly but surely towards more and more filtering, which I am not a big fan of. It might be because I was in the scene from way back during the DivX 3 days, but my mindset when encoding video is and has always been to reduce file size while trying to preserve the source video. Nowadays, the mindset of a video encoder seems to be to try to find a magical set of Avisynth filters that "improve" upon the source video.
My complaint isn't totally against deinterlacers because I agree that 60 FPS is better than 30 FPS for pure interlaced sources. I'm glad to see more and more encoders realizing the smooth motion that 60 FPS videos provide, but this is something that I have been preaching for a very long time, just in a different way. Like I said above, I prefer to encode interlaced and deinterlace during playback. Again, it's all about the different mindsets: encoding interlaced (preserving the source) vs pre-encode deinterlacing to 60 FPS ("improving" on the source).
My real complaint is with noise reduction filters. Time and time again, especially with fansubbing groups, I see videos that have been over-filtered, completely destroying fine detail and giving the video a really muddy look. I understand the need for noise reduction filters when dealing with sources that are overly noisy or blocky, but I don't really think it's necessary for most video sources. People tend to forget that the human eye likes a little noise in the video. It likes to see that very fine detail, yet so many encoders filter it out in their attempts to "improve" on the source video. That's why I really like the x264 developers. They understand what the human eye likes to see, and their psychovisual enhancements (AQ, Psy-RD, Psy-Trellis) are all designed to help preserve the fine detail found in the source video. Again, the key here is preserving the source.
Maybe I'm just "old-fashioned," but I can't justify spending so much CPU time filtering video when my current encoding settings blaze along at 2x realtime and still produce high-quality encodes.
BTW, activating hardware deinterlacing during playback is pretty simple in ffdshow:
It reads the flags in the video, so it knows when to deinterlace and when not to. I'm not sure how to do it in other decoders, but it's probably even simpler than this.