A push-pull config offers better initial performance, but once the radiator clogs with dust, for example this dust buildup on my kraken x40 caused a 5C (I use the silent fan profile) increase in temperatures
http://i.imgur.com/1DUmKTl.jpg while a push- pull config only lowers temperatures by a small amount, often less than 5c. While I could easily do a push pull, it will be difficult to clean the radiator, and thus it will be cleaned less often, which will mean that it will consistently perform worst than if when I do a pull config (at least in my case where I clean the radiator every few weeks.
Here is a good video detailing the benefits of each config.
https://www.youtube.com/watch?v=UyC3lZ5WFMk
another video with some benchmarks
https://www.youtube.com/watch?v=Kk7JMOcypus
Most of the all in one coolers support push-pull configs by simple screwing in fans on both sides. The issue is that you will likely go longer between cleanings, and with push-pull only offering a small temperature improvement over just pull, you will end up with a larger temperature swing, and depending on the air quality, within a month or so, you may end up with less cooling performance than with a pull config
On my case, I have the basic mesh air filters and while they do capture some dust, they still do not prevent the radiator from getting clogged. (and case fans do not have enough pressure to use a HEPA filter)