The best way to answer your question is to refer you to Bob is the Oil Guy. (And boy is he.) While you can find literally everything you need to answer your question and more, the site can be a bit tough to chew through.

Oil Filter Forum is where you'll find the raw answers to your questions about oil filters, and the rest of the forums contain tons of information, but with 480 pages of stuff, you could take days to find it.

So I offer you a page I bookmarked when I was still employed by Jiffy Lube and have found to be reliably correct in 99% of situations. Oil Filter Study, He talks about the oil filters, cuts them open, gives a number of statistics about them, and then provides his own opinion based on an examination of their construction. But! He doesn't have the K&N filter on the website yet. Sorry. I'm gonna go ahead and tell you though that comparing a metal-mesh filter like the K&N reusables (I assume those are the ones you mean) and a paper filter like a FRAM is gonna be tough to do. However most people will tell you that the FRAM is bad. The Mobil's are indeed fine, but I have done tests myself and seen there is no measurable difference in pressure from the Mobil's to factory OEMs on a properly working engine. YMMV, but I hope you can at least understand why none of us would be reliably able to answer your question with anything but a suggestion of what we use.