Just to throw two more cents in there: just my own personal opinion, I would rather throw 100 percent of retained dirt away as opposed to washing out 90 percent. The advantages of a washable element in a combat situation are more than obvious, but fortunately I don't find myself in those situations. Performance issues are a valid concern though, the problem is finding the data. If there were quantifiable data so as to compare the micron rating and beta ratios for given pressure drops across the elements as well as dirt holding capacity I would definitely let that influence my decision, until then I'm a throw it away kinda guy.
A question though, what kind of effect do you think giving the air compressor it's own filtration so as to not rob manifold air would have? Effects on naturally aspirated as well as boosted?