[crushu]

I have tried K&N and other Cotton filters in 4x4's, and they do flow more than older standard filters, they do let a lot more crap in. The oil soaked foam filters don't let much air thru, but do block a lot more dirt (we dynoed a IMCA with and without Foam filter, there was a 10hp gain (at the wheels!) with a clean cheap paper filter (14" x 4"). In speedway, there is not much dust, so the better filtration was not required.
In the dust here in Australia, the K&N style filters get a bad rap, but they do make more power.

I guess is you are in the city, they would be better, but not in rural areas.