One thing I am noticing is the Fogger seems more able to wick like crazy then then the Kayfun, and because of that I am able to run quite a bit more wattage through the same OHM's on the Fogger then the KFL without getting dry hits.
It may just be the way my KFL is built right now, but yea the Fogger seems to be able to take a lot more power and keep up with the wicking.
Because of this I am also going through juice twice as fast it seems.
My current KFL build just sips on the juice, and makes for a little dryer vape, the Fogger on the other hand chugs the juice, and delivers a nice rich cloud with lots of flavor.
I like both units for their own reasons, and I do think some juices will taste better in one or the other, based on coil saturation.
The biggest difference I notice between the two is the "sweetness" of the flavor is definitely higher in the Fogger. If you have any juices that you like to taste sweet, definitely try them in the Fogger.