So in a nutshell, what's the difference between the 2 commentaries? I would not buy the P&S, and in fact am waiting on delivery of the gift set. But I am baffled as to why on earth they would record the second commentary. Is it just because of the additional material in the UR cut? Worrying about matching the commentary run time to the movie run time just doesn't seem like enough of a reason to think of another 2 hours of things to say about this movie.

Rarely on either track are they really talking screen-specific. There are some bits that are repeated but there's lots of different comments as well. For example at the end of the track the same bit is used to end the conversation with Christina Applegate, but beforehand, each track is different as to what they're talking about.

well on the unrated track

IIRC... that makes up more like 90% of the commentary track.

On the PG-13 version's commentary track, it starts out with Adam McKay and Will Ferrell just BSing about their free time, talking about meth labs, hookers, all kinds of jokey over the top stuff. Then a studio tech comes in and asks if they knew they had started recording.