Still a longevity thing...With me being sideways stupidity...I'd rather not change the plugs often...unlike the 3800 that took me all of ten minutes, or your V that probably has ignorant amounts of engine bay room...especially would be a cake walk with the manifolds out.
Go with whatever, it's your car...I'm not trying to steer you one way or the other just stating what I've seen that's common or what has been proven to work. I'd venture to think upgrading the wires would make more of a difference than NGK this or ACD that...but that's me.
As for specific price, I never looked at the TR55's, as I only ever ran AL's in the GTP. I know the 41-110's run on average about $6~ a plug.
