Giving students the ability to rate teachers can have its issues. I got two ratings on a site that did that, one praised my teaching and the other simply said I had a nice bottom. MY fellow teachers claimed I posted the second one.
Comparisons and advocacy
Why Moodle may not be the best solution for a paid online training site
Geoff Scott has an interesting perspective on this. https://www.westernsydney.edu.au/staff_profiles/uws_profiles/emeritus_professor_geoffrey_scott
He thinks a good determinant of real value for courses and teaching is to survey graduates.
Then you hear this: "Well, this course was bad at the time and I hated it but now that I am out in industry I realise it was the best"
Survey the student DURING the course and you hear "Oh, I hate this course, they make me work and think too hard"
Marcus has got data in these ratings sites. What they mean is not easy to determine.