I'm curious: for those of you who have used the 75/90 Grandagons in both f/4.5 and f/6.8, just how important was that extra stop of light to you out in the field in terms of having a brighter GG to work with?

I'm in the process of sifting through wide angle options for the Horseman HF, so all things being equal, the 75/6.8 with its 58mm filter seems the logical choice, but since I do a lot of work under canopy, "more light" is always appreciated.

Any thoughts appreciated...