In my experience it depends upon the type of defense you run and the players you have. It also depends on if the offense is usually going short...or going for the deep stuff. I will often use Always Run, but I never have used Always Pass.
THEORETICALLY, the Always Pass setting puts your DBs well off the LOS to give a big cushion. Always Run puts them up closer to the LOS.
My logic says that if I have speed in the secondary, then I can probably move closer to the LOS and still not get beat deep. Without looking at your players, I would think something like Nickel Balanced Balanced might be a good choice.