I would say 9 out of 10 times, the nose door isn't needed...but the few times that it is, having this option enables a significant amount of revenue to be earned.
For example, on a -200F we once unloaded a sailboat mast that was 170 feet long...and often there will be pallets long enough that loading thru the nose is much faster than using the side door and turning the corner there.
Lufthansa had a neat system at JFK where you would taxi the plane right up to a hangar, the nose would actually be inside (or we'd get towed in, can't recall), door would open and they'd shoot all the pallets out the front and right onto big shelves for sorting, or something to that effect...much faster than K-loaders out the side door. I am sure this was pretty expensive to have a building set up this way, though, so likely not often duplicated. And the tall pallets, if aboard, would still need to go out the side door.
Having both doors is the way to go IMHO, though we did well with our -100/-200/-300SFs too. There were a few planes (World Airways was the customer I believe) that ONLY had the nose door...though this would limit you on pallet height for sure...not real popular I imagine. There is a slight weight penalty of course but I am sure this is offset by the increased utility...
TT