The verdict
If you are testing an idea or sell occasionally, I'd pick Gumroad. A product can be live in an afternoon, and one that sells nothing costs nothing. If the course is the business, you expect more than one, and you want your own branding, reports on what learners do and community spaces, pick LearnWorlds. The cost shapes differ. Gumroad's cost follows revenue and stays that way. LearnWorlds charges a fee on each paid enrolment on its entry plan, and its higher plans do not, but they have learner caps. API access and webhooks sit on the higher plans, so check that before you plan any automation.