And another thing... while the K&N might let through more dirt in laboratory tests, I ran my V-strom on one for 6.0,000 miles with no issues. That bike is still running great for its new owner. I once drowned that bike, filled up the airbox with water, and the K&N ensured that nice clean filtered water went into the engine.
Whereas a paper filter would probably have disintegrated and made a hell of a mess.
I'm running a K&N in the Super Tenere now and it's seen some hellishly dusty roads through Bolivia and other places. I give the inside of the airbox a light coating of grease so that if there's dust getting through, some of it should stick. I never find any.
I think one of the keys to with the K&N is NOT to clean it. My theory is that once the pores a blocked by some dust, it filters better than when clean. I just cleaned mine for the first time in 16,000 miles, was really dirty but wasn't noticing a dropoff in fuel economy or anything like that. K&N say it can go as much as 50,000 miles between cleanings, but I wouldn't let it go anywhere near that far.
I'd considered using the foam filters for this trip (in fact I had a set), and I'm sure they do filter better than the K&N, but they need frequent cleaning in dusty conditions and the maintenance overhead is too much for me when there is riding to be done!
Oh and I don't believe for a second that they "flow better", but that's not why I have one.
Would like to see the laboratory comparison between the K&N and the Dyna filter and other similar reusable filters - anyone know if this has been done?