I get three and would rank them Muzzleloader first, and then the other two are tied for second:
Muzzleloader Magazine
Seems most real, traditional, 'down home', history articles, low quality B&W photos & sketches, inexpensive, bi-monthly;
Muzzleblasts Magazine
An awful lot of the magazine is devoted to the NMLRA organization, Friendship shoots, advertising, and gunbuilding...so-so quality photos & sketches, twice as expensive as Muzzleloader Magazine, comes monthly;
Black Powder Hunting
A scattering of articles that might cover any aspect of muzzleloading, but seems to lean more towards inline type ML's and modern products rather than traditional...high quality glossy paper and color photos, more expensive than Muzzleloader Magazine, is bi-monthly.