Yea, interesting comparison.I have a feeling that my groups go quicker than average.
Currently, we play weekly for about 3.5 hours. We complete around one hardcover chapter per session. We're currently playing Curse of Strahd. We have played about 7 sessions. I am assuming 1-2 sessions before they're ready to go to the Castle. Will probably spend around 4 sessions in the Castle.
That means Curse of Strahd will have taken us about 12 sessions to complete. The previous time I ran it, it took 6 months of 2 hour sessions - so I think that's about the same.
To toss in more anecdotes, my groups very rarely do published adventures, but we did do Curse of Strahd. It took us about 30 sessions to finish, each session being roughly 3-4 hours.