Our terrain is wetter than wet, but I don't notice a huge difference until after the first shot is fired. Somehow it just seems to be harder to clean and dry the pan and frizzen enough to keep the 4f from turning to goop when priming for a subsequent shot. It's not a bed of roses with 3f either, but more do-able for some reason. No science behind that and I've never heard anyone else say the same thing.
Multiple shots? All that probably isn't an issue if you're a one-shot deer hunter. But I do a lot of small game shooting with a dozen shots a day not unusual.
One more point- I like using 3f for prime (or even 2f in larger cals) because I don't have to carry a separate horn or charger for priming. That's a convenience point, but again an issue when you're doing lots of shooting in a long day.