I went with the Volant because, lot alot have said, it's a sealed box minus the hole in the bottom for a possible future air scoop. I've got a friend who races his 06 Chevy 1500 and used to have one of those direct ram air intakes when you remove your head light for at the track and he switched to a Volant with the air scoop and likes it alot more.
Also, all of our John Deere tractors have a powercore filter exactly like the Volant one, just shaped differently for obvious reasons, and they are hardly ever dirty. Granted it's because they have some sort of turbo suction to help pull the dirt out but they are never dirty no matter how dusty the fields get. The K&N is going to have an oiled filer that's just going to get dirty and gunk up and limit air flow while the powercore you just blow out and put it back in.