Hard to say which one is the best because any one person is going to sign up with one and they won't have anything to compare it to. So ranking them is a little difficult unless someone pays for each one and takes each course. Not sure what value someone may get from that other than a good search ranking on Google for a blog on their website.
That said, I went with Pilot Institute and it was great. Just passed the exam this week with a score of 93%. There may be a better one out there, but I will never know because it doesn't make sense now to sign up for another course.
Not to undercut PI on price, but check for any discount codes or affiliate links that may be out there. I used an affiliate link of a YouTube couple that got the dreaded call from the FAA that they were operating their drone illegally by using footage taken with it in their YouTube videos. They weren't fined, but their video was pretty informative, so I used their link to help them out a little.
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