Alright, intial BD transfers were done poorly and now BD has the stigma, among people who have never seen the two formats, that it doesn't look as good. BD transfers have come along way. Look at Black Hawk Down, Tears of The Sun, Kingdom of Heaven, MI:3, X3, Underworld Evolutions, upcoming Fantastic 4, etc. These titles blow away the early BD releases.
BD isn't using MPEG-2 it uses VC-1, AVC, and MPEG-2. This give the studios a choice. The cost of converting the MPEG-2 setup to VC-1 is a good bit so some studios decided they would stick with MPEG-2. BD50 will make it possible for MPEG-2 to look good, but the studios can also decide to switch to either VC-1 or AVC.
This is the first I've heard of the PS3 freezing while playing BD movies, but I can say that the PS3 has been on 6 hours and hasn't hiccuped once, playing games and TN.
Also keep in mind that updates to the PS3 can be made to improve BD playback.
You're comparing different movies. If you wish to make cross platform PQ comparisons, you need to watch the same movie on both machines (such as Mission Impossible III).
Keep in mind Mission Impossible III is MPEG on Blu-ray and VC1 on HD-DVD, so a Warner movie with VC1 on both will be a better comparison!
as you can see even with the same title a review can be difficult when trying to compare the hardware.