I'm coming in 3 months late to the discussion but found this thread in a search... I'm in a similar debate myself. @missioncontrol did you end up getting one? Which and how is it?!

I started with the Mark XX, having no interest in a "Big Pilot" because of the price and seeing it more as jewelry than 'tool watch'. I've had the XX for a year now, and- don't get me wrong I love it- I'm craving the BP43. The XX wears great, super comfortable, looks sharp, but can go anywhere and do anything with me. But after a while I just feel like it looks small. I only have a 7" wrist, but what I think is going on is, because it's a pilot flieger style watch, what I think looks "right" would be at least somewhat oversize vs whatever other style watch size I would wear. I would say 40-42mm is my personal ideal watch size... but then a flieger should be (or feel, or appear) just a little bigger.

I also noticed thickness- or lack thereof with the XX- matters. I have always thought thinner watches are better, and since I'm pretty active and outdoorsy I liked how think the XX is. But after a year, I feel like a flieger isn't a flieger if it isn't at least a little bit chunky!

But here I am, already owning the Mark XX (technically two, because I had blue and just bought the black and haven't sold the blue yet LOL)... and there are times I love the wearability and versatility... so yea, conflicted.

Even though they look so similar, the Mark and the BP really are quite different wearing experiences! (IMHO)