(to the mod above, I'm not comparing the phones, just the video implementations, not trying to start a flamewar)
The sharpness clarity of the Desire 720P seems higher than the Nexus One so far, but I have not seen any Raw video files yet so everything has been re-encoded by YouTube (10 Mbits, 30 fps). The video looks a bit too stuttery to be 30 fps so I'm wondering what the real framerate is. Also I'd imagine a lot of people doing the HD recording don't have high-class microSD cards, which is a problem for phone manufacturers wanting to put HD video recording on there phones since difference write speeds will result in a such a drastically different user experience between people with differing cards. That may be one of the reasons the N1 didn't have 720P in the first place because Google didn't want to have to say "Yeah, you can record HD, but you'll have to buy a Class 6 card as well because we've only given you a (still quite fast) Class 2".
@DesireableHTC - If you have VLC, you can open the video file with it, and go to Tools > Codec Information. This should tell you the framerate.