Both of these learning management systems have their issues. Neither should be considered for a production online course website for different reasons. Sensei is not really being developed and LearnPress is not coded well. A quick glance at their reviews is enough to scare anyone away. I recommend you instead consider LifterLMS if you are wanting a free LMS and LearnDash of you want a paid one.
LearnPress Vs Sensei 2019
LearnPress is a comprehensive WordPress LMS Plugin for WordPress. The core plugin is free and there are many free extensions and paid extensions available.
Sensei is a learning management system for WordPress from the makers of WooCommerce. WooCommerce was acquired by Automatic, the parent company of WordPress itself.