I don't know anything about portolan maps, but Variation B feels more balanced to me. The map scale does seem like it could do with a bit more room there, but I like that it and the compass are in the same corner so you don't have to keep zooming in and out to find the map references. I also like that they're diagonally opposite the cartouche.

I love the border and frame. I never have the patience for them so my own maps tend to just have a thick black line around them. ¬_¬ Yours lends the map that historical feel without being distracting.

The only suggestion, and I don't know if you want to muck around at this stage of the game, is maybe having less of a "glow" around the ships. It's quite large at the moment and covers up a lot of the grid lines. If the current glow is, say, 20, I'd go with some thing like 5 at most instead.

The labels are a bit difficult to read, too, even at 100% zoom. I'd probably pick a different font so they're easier to read at this size for future maps. (I wouldn't think you'd want to edit them now.)