"can't make my mind up between then SK72 and 70HR so an interesting discussion."
from all my readings, the conclusion seems simple
Two good lenses
if lightweight is important, the the 72 wins
if large image circle is important, then the 70HR is the way to go
There's nearly no distortion with the 70, but anyway even with the 70, the distortion is minimal !
Unless i'm finding a good deal on a 72, i will go for the 70 for stitching !
In general use, this lenses are similar...
Wide open, the 70 is supposed to be a tad better.