None is fine for Phoenix PD. Phoenix PD itself is simulcast A only, the same thing, over the same frequencies, and the same control channels, on each site, all broadcasting at the same time. You won't be roaming, your radio will be fighting over three or four of the same thing coming in slightly out of phase and depending on your location it can get crazy as you probably know.
Maricopa County Sheriff is an example of where you could use multi-site. The same things are sent from two sites (white tanks, and thomson peak), but they use different control channel frequencies. This is where you set your scanner into roam mode. That way when you get closer to one or the other, your radio is checking and sees that one site has a better signal and switches over to that control channel / site / frequency. It works well, but I hear the white tanks site burned down, so I don't know if it will work at this moment. I live right between the two and without moving around in the valley I can't tell if it is working, and I haven't done that for a while with the 500.