The 140 and 150 are two entirely diferent lenses with diferent uses: the 140 is is high quality macro, the 150 is a Soft Focus that gets sharper as it is stepped down, a bit like an Imagon.
The real use for the 150SF is for portraits and weddings.

I love these shots !

I have the 150SF (on purpose), but now you made it clear to me that the 140 should be on my list.... THANKS !