Hi there,
Just to clarify, you are not planning to apply to an MBA program currently, you are just curious for additional opinions on the NYU digital marketing certificate? In general, certainly additional education and certifications in areas that will benefit your career cannot hurt, and can add more to your resume and employability.... but to learn more about a specific certificate program like this, even at a reputable school like NYU, I strongly suggest you a) ask lots of direct q's to the admissions officers/professors of the program before applying, b) ask to be put in touch with current students and alum of the program (generally admissions offices will do this), and c) if possible contact some recruiters/HR offices at companies you may consider applying to in future, and get their feedback on it.
Good luck!