As most here know FSP power supplies are my third favorite thing in the world (Ok, I lied, they are second). Either model should be fine for your consideration, but the new 120mm model is better. They have shifted some of the capacity to the 12V line on it as compared to the BNx. The BNx series 350 has 32A on the 5V line, and 15A on the 12V. The PN is rated at 30A on the 5V line and 16 on the 12V. This is not a huge difference.
It is entirely possible that they are the same design nonetheless. Either unit will put out well beyond 16A on the 12V line, so there is no guarantee Fortron didn't just adjust the spec. I really like the 120mm fan version, but either should do fine. I have the BNS in my rig.
I take it you know Newegg has the BN for $32, and xpdirect has the PN for $48.