I hear you, but you are making it too complicated. What "your style" of RB is kind of irrelevent. It's who is the best and most productive RB in the sytem that they are in---that is really the only non-subjective way you can judge then. Also, Westbrook is a great all-around back. He can run inside and out, can block when needed, is an amazing receiver, etc.
Portis had the overall best season of the group last year due to injuries by some of the others.
On the other hand, I agree it's not so straight forward now that Westbrook is starting to break down a little. Great move by Philly in drafting Shady McCoy.
Bottom line, the NFC beast has some amazing running back on all 4 teams. All four teams should be happy with who they have.