Need help understanding the video codecs.

[Grisle]

I'm ignorant when it comes to the difference between the video codecs. I was reading a review of M:I III on dvdtalk and here's what they said:

Video:
The Mission: Impossible III Blu-ray is encoded in High Definition 1080p format using MPEG2 compression on a single-layer 25 gb disc. Why Paramount has been using MPEG2 on Blu-ray when they already have (more efficient, and equal or better quality) VC-1 encodings prepared for HD DVD that could be ported over is anybody's guess. The movie is presented in its theatrical aspect ratio of approximately 2.35:1 with letterbox bars at the top and bottom of the 16:9 frame.

http://www.dvdtalk.com/reviews/read.php?ID=24719

I've been reading that Blu is getting some ports from Warner and it's not quite showcasing all that BD has to offer. Is this reviewer just an HD-DVD fanboy or is the video better on the HD-DVD version of M:I III? What would the direct comparisons be on VC-1 vs MPEG2 or MPEG4? I thought MPEG 4 was the best, but I guess it all depends on the bitrate. Can anyone help me understand so I can tell if an upcoming BD has the best video available?