With Brooks saddles it seems that one of the more important determining factors in choosing the right saddle is the height of the handlebars compared to the height of the saddle. If the bars are below the saddle, you'll probably want something more narrow than a B17. If the bars are at or just above saddle height, then a something like the B17 is probably a better bet.

Lots of probably's in that paragraph. For good reason. The advice might not be right for you. It's what what works for me though, and seems to be conventional wisdom.

One other thing to consider is that Brooks have notoriously short rails. It might make the cockpit a bit more cramped for you if you tend to have your saddle back as far as possible.