I can make a comment on this, having recently bought a bow...

All I can say from test-firing several different bows at the pro shop, in both 65% and 80% letoff is that IT DEPENDS. Some of the bows had me creeping back at 80% letoff and some were just fine. I think if you could see the draw weight versus distance curves for each bow at 65% and 80% letoff you would be able to tell from the graph which bows would be best for you. Seems that the higher FPS rating a bow has, the steeper (and shorter) the curve from full weight to holding weight is (and therefore the shorter the valley). Correct me if I am wrong there please

I ended up buying a bowtech tomkat, and this bow feels really good with 80% letoff. Should I change my mind, I can swap out the module and tweak the post setting on the cam to get 65% letoff with about 30 seconds of work using their handy chart.