Montblanc is a brand which I feel is being refreshed and their brand pedigree is getting better. Being under the helm of former JLC manager, I feel their design is getting timeless. However, their brand is still relatively new in the horological world.
Go for BR if you like aviation and their design only.
Longines has a longer history and their heritage line is just beautiful. Oris has some good lineup but Longines and Oris as brand has too much in their line to be considered a true top tier. They have something for everyone which I feel has its pros and cons.