The Pro guard 7 has 7 elements (5 cotton, 2 synthetic). The "regular" filter has 4 cotton elements. the obvious is you will get more air flow with 4 elements than 7 giving you more power, and along with that you'll also get more dirt in your engine with the 4 element.
I have the pro guard 7 filter in my truck. I'll sacrifice the performance for better filtration and longer engine life.
Check my readers rigs for a pic of my old airaid system and my new AFe system.