The ones on the left were round mottled metal ones, and the ones on the right flatter textured brown plastic ones. I decided that the metal ones took the military inspiration slightly more literally, and the brown ones were a little "warmer.
I spent a very long time mulling over my choice, including calling a friend for a second opinion (with the lady in buttonmania being very patient!). In the end I went for the brown ones, as I like the slightly less literal interpretation of the military inspiration.
I'm hoping to get it finished this weekend - I have the buttons to sew on, buttonholes to do, and lining to sew in left to go... that's doable, right?