The 5w30 is sufficient for most applications. I'd only use the 0w30 in climates with super cold temperatures for easier startup. For where you live, it won't make much of a difference, the 5w30 may actually be more shear stable.
However, there are a few exceptions. One is the GC, which is an excellent oil. The second is the Series 2000 0W-30. Yes, even though msparks is selling everything at dealer cost for March/April, the stuff is still $75/case where the ASL 5w30 and ATM 10w30 is only $53.40/case.
So my take? I think that neither the GC or the Amsoil Series 2000 0w30 is worth its cost. The ASL 5w30 or ATM 10w30 is clearly the winner, unless you want to go with the M1, where my preference is the 5w30, but the 0w30 should be fine as well.
Michael