My first choice would be PP because it's the only A5/B5 oil sold in the US (and possibly true for Canada, too)
My second choice is Castrol. It's A1/B1, supposed to be reformulated to meet A5/B5 again soon, but still good for long drains.
Third is Synpower. It's just not as good as Castrol and PP (or M1) and not worth the same price as them. No ACEA, and it doesn't even claim HTO-06 standard that the others do meet. In fact, there are even cheap syns that meet HTO-06 (such as QSUD and Havoline ProDS syn)
Napa Synthetic is rebranded Synpower, but for the same price, just get the name brand. Now, if it was on sale for $3/qt, then I'd use the Napa (that's most of the appeal for Napa syn--it's Synpower at a lower price). I believe Napa Synthetic and Synpower to be worth the US Napa sale price but not worth the same price as PP/M1/Edge
NOTE: if M1 5w30 was on sale at the same price, I would rank it between Castrol and Synpower.