Which PSU to go for?

As per my question about a year ago in this thread, http://ift.tt/1BUKnPb, I'm going to be building it in the next month or two. These are the specs I'm planning



Intel Core i5-4440

AsRock B85 Motherboard

8GB RAM

1TB HDD (more drives will be added later)

CM K282 Case

and possibly a Radeon R7 270/270X or R9 280



Things have changed quite a bit since then and more great units have come down in price. I've limit my choice to either a SeaSonic S12II 620W 80+ Bronze or the Cooler Master VSM 550W.



Considering both units have the same price, which one would you buy?



Thank for any help.

Which PSU to go for?