Could you please be more specific?
Vague generalizations aren't very useful.
Thanks
Sure, it is actually quite simple.
DFK goes through fire-curing process with hardwoods, which changes its chemistry quite a bit. On the other hand, burley is air-cured. Burley creates a more alkaline environment when smoked, which can irritate your tongue. DFK, thanks to fire-curing, has a more balanced pH that's closer to what your mouth is used to. Fire-curing has some extra benefits. DFK picks up compounds from the hardwood smoke that can actually soothe your mouth and protect it from irritation.
DFK indeed may be more nic-loaded, but it's not as "available" to your mouth tissues as the nicotine in burley. Burley hits you fast, which can be part of that tongue bite feeling, while DFK takes its time.
Pairing burley with lemonade made from some actual lemons (a bit of citric acid will help you balance out the alkaline environment burley creates) or blending in some DFK will help.
UPD: nicotine bioavailability also hints why DFK makes a perfect night smoke, while burley is more a work day thing.