You may wish to ask this on the MF page: http://www.photo.net/bboard/q-and-a?topic_id=35(posted 8622 days ago)However, I'll give you a quick answer here. I have both lenses in the Rollei SL66 mount. The 150 is the same design but there may be detail differences between the 80's.
The 80 is a symetrical gauss derived design which gives it the edge when close focussing. The 150 definitely is not as good in this regime because it is a simpler design and has been optimized as a tele lens. I think this is a fine characteristic to have for a portrait lens. Other than that the lenses have similar MTF curves (see the H'blad website) giving similar resolutions. My experience has born this out.
BTW, look at the curves for the older 50 and the 250. I think you'll see they're not as good as the 80 or 150; something that some users have commented on. I've not heard of any complaints on the 150 except when shooting up close.
Cheers,