Re: Who has the best defense in the NFC West?
I'd choose the 49'ers because they have the best front 7 in football and that's what I believe matters the most.
They have the best inside linebackers in the game, bar none. Nobody is even close to them. Seattle has good linebackers, you can't help but be impressed by KJ Wright and the rookie Wagner....but they aren't Willis/Bowman. Arizona has a similar type player in Washington to the 49'ers duo, but his running mate is nowhere near that level.
They have a legit sack monster in Smith at OLB, and very good complimentary players at the other OLB spot. Arizona does not have that Aldon Smith type player.
Up front they have an elite defensive lineman in Smith and depending on how you feel about McDonald, another star as well. Sopoaga is very stout and does his job very well. All three teams have an excellent front, it's the linebackers that separate the 49'ers from Seattle & Arizona in a very clear way.
If you value secondary play more than Seattle might be your pick.