From my reading I got that pull was slightly better, but not by much. Perhaps wherever I read that had incorrect information. And your point about cleaning is something I had never thought of.
Edit after doing some more research
Turns out i was incorrect about pull being better in performance, here is a quote from rubix (water cooling guru) from another thread:
"With 1500+ RPM fans, you want PUSH on a radiator. Less than 1000-1200 RPM, you want PULL on a radiator.
Push/pull on a radiator does not have anything to do with push/pull in reference to internal/external case orientation...could be either, depending on actual airflow direction.
Coolest air over a radiator is best, even if it from outside the case. If you have great case airflow, it really shouldn't matter if these fans are moving air inside or outside the case, as long as the fan movement over the radiator is PUSH."
And this test also points to push being slightly better than pull alone:http://martinsliquidlab.org/2012/01/15/radiator-shroud-testing-v2/