I once read a filter test by Dave Vizard in which he tested all the popular manufacturers filters and filter types, from paper to foam.

The K&N filter came out tops. There wasn't a huge amount in it between the top filters in peak flow but he also tested the filters again after 1000 road miles and the K&N was out flowing its rivals by a huge margin! Seems as the K&N gets dirty its performance doesn't drop off nearly as much as its competitors!

I would go for K&N every time. Very easy to wash and re-oil.