Mil-spec doesn't necessarily mean better, it simply means the specifications the military wishes the producer to adhere to.
BUT, the one good thing about mil-spec is it is a known set of standards of production. IOW, you know what you are getting, exactly. If you buy a mil-spec replacement part from ANYone, it should be exactly the same as the part you are replacing, regardless of who that part came from.
When standards are left up to the producer, you get.... what exactly? How does it compare to the part you are swapping out? Better, worse, what?