Such questions are very difficult to answer.
Many students do not take such courses
Of the students who do take courses, it is highly unlikely that they have taken courses from multiple test prep companies.
Your best bet is to first assess your strengths and weaknesses. Please do take a diagnostic test without any preparation. Do your best. The results will give you an idea of the areas that you need to work on most.
If you need to start from the very basics and you have more than 2-3 months to take your test, I would recommend GMAX Online. I have personally reviewed the course for GMAT Club and the review is posted on the website. I have only heard good things about the course. Again, I am in no way suggesting that the others are bad.
To summarize, try to first understand what your specific needs are. This will help you ask the right questions when you call or meet someone from a test prep company.