First, tell D2L that you are considering switching to Canvas. D2L is losing its market to Canvas, so they need to get your message.
Then, if not successful, you might consider getting a faculty team to evaluate a switch to either Canvas or (and now include) Moodle. This is procedural because most faculty don't know how to evaluate the difference, and it is too time involved. So take your pick, then wine and dine these faculty (and administrators) to your preference.
If you are an administrator and end up with this stubborn supervisor, consider changing jobs.
If you are a teacher at this school, consider running Moodle on your own.
If you are looking for one major and important difference, you might want to collect a variety of syllabi and focus on grading. Pick the LMS that can best satisfy all grading schemes. If you are at a college with an engineering program, make sure to include syllabi (and grading schemes) for these engineering professors.