Udemy's appeal for CISM prep is the price — self-paced video courses at a fraction of most competitors' cost, often discounted further during sales. For an exam covering four domains where the material is governance-and-program-management-focused, the trade-off is that you're relying on one instructor's coverage with no diagnostic, no readiness tracking, and no way to know if you're actually prepared until you sit the real exam.
Course depth also varies more on Udemy than on a single-provider platform, since quality depends entirely on which instructor you pick. Candidates typically cross-check a course's domain coverage against the official CISM exam outline before buying, since there's no built-in way to verify a course is comprehensive.
The deeper gap is diagnostic: a Udemy course has no way to tell you which of the four CISM domains you're actually weak in. Edureify's Diagnostic maps that on day one, and the Readiness Score keeps updating from there — so you get a specific, evolving answer instead of a vague sense of how far through the videos you are.