The P3 system is mega rad if you're really into highly aggressive shoes with a steep downturn. I've had a couple pairs of very aggressive shoes (think 5.10 jet7) that did not have the P3 system, and after about 6 months or so they were almost completely flat.

My advice is to just go with whichever shoe works best on your foot. If it happens to be a shoe with P3, lucky you! But don't force your foot into one for that sake alone.