Udemy's appeal for PSM I prep is the price — self-paced video courses covering the Scrum Guide and sample questions, often discounted to a few dollars during sales. Since PSM I doesn't require an accredited course to sit the exam, Udemy is a genuinely common starting point, but a video course has no way to tell you which Scrum concepts you're actually shaky on.
Course quality also varies more than on a single-provider platform, since anyone can publish a PSM I course. Candidates typically supplement with the free Scrum Open Assessments from Scrum.org regardless of which paid course they choose, since those are the closest public proxy for the real exam's difficulty.
The deeper gap is diagnostic: a Udemy course can't tell you whether you're weak on Scrum theory, roles, events, or artifacts specifically. Edureify's Diagnostic maps that on day one, and the Readiness Score keeps updating as you practice, rather than leaving you to guess from a completion bar.