Given your dimensions, going with the narrow one would be a huge mistake. You will regret it.

Here is why:
The narrow B17, also known as B17N, is indeed nominally 155 mm wide.
However, its width at the widest spot measured in between the rear horseshoe-shaped metal frame is about 106 mm. Anyone with wider-spread sitbones would have them riding onto the metal frame, resulting in lots of misery.
My own sitbones measure 96 mm, and I have been riding a B17N for some 3 years now. The saddle is very comfortable (after I spent about 700 miles in the beginning of our relationship breaking my ar$e in), and still harder and stiffer compared to the regular B17. But it is not for sitbones measuring over 100 mm.

Your call...