I'm sure many of you are already familiar with Bob the oil guy. He is a respected chemist that hosts a website to dispel myths and provide proof on which products work and which do not..
He recently did a test on various types of intake filters. Gauze, foam, paper..
His test is unique in that he places a second filter behind the filter being tested. This shows what dirt makes it thru the intake filter.

Here is the link:

Filter tests

Interesting results... Seems paper is the best in trapping dirt and flows almost as well as others that don't filter too well... A good read for sure..