Have a lovely old IF ED 300 mm f4.5 Nikkor which is great on the Df for tripod work and ok for handheld shots on land. It is not so good for photos taken from my boat however so a modern VR lens is tempting. Subjects are other boats/ships, marine wildlife/coastal scenery- lighthouses etc, not really birds in flight or anything too demanding. The new 300 f4E PF lens looks to be ideal but am also tempted by the 80 to 400mmf 4.5 -5.56G zoom. No doubt the Sigs and Tammies are fine lenses but I will prefer a Nik. I have 85 mm f1.4 and 180 mm f2.8 so a bit of overlap with the zoom - the only benefit would be less salt air getting into the works from changing lenses at sea.
Have never had a zoom before and the Df might object (if I asked it). What does the panel think?