It's certainly not hard to fall for intensive marketing hype - but it still amazes me how many people do.
The proof is in the end result: if anyone wants proof that oiled cotton-gauze filters are sub-standard, install one, ride the bike 'til the next service interval, then remove the filter and run a finger around the inside of the airbox. See how much oily grit has passed unhindered through the filter and into your airbox.
Now ask yourself: how much more grit bypassed the airbox walls and got sucked through the cylinders?
Now, perform the same test on a mate's bike where the standard BMW paper-element filter has been installed since day one.
Oiled cotton-gauze filters claim to give the best of all worlds, and they sell in large numbers because they appeal to people who believe you can get something for nothing. They are wonderful things for use on circuit-racing engines which are rebuilt frequently. But on the road, where you will never notice the difference in day-to-day riding, they serve only to facilitate more frequent engine-rebuilding.
For air filters, my first choice is ALWAYS a good-quality paper filter.
If you must use an aftermarket performance air filter, my preference is for high-quality polyurethane foam filters, like the Unifilter. These use a denser, more tightly-spaced filter matrix, and a much stickier, tackier oil that traps more incoming dirt.
