Hmmm, that would be a hard question to answer, you' have to know what "Best" means to you.
For some "best" means most likely to help them pass.
For others it means most value for your dollar,
For others it means comprehensive, (IE does it cover "it all"),
And yet others would think "best" means an enjoyable program and an engaging speaker.
It's really up to you what your "best" is.
Of course for most, it's a mixture of all of the above, and finding one program that is the "best" in all categories can be challenging.
Unfortunatley, it's hard even for your peers/colleagues to answer this question, because most everyone has only taken ONE review class before their exam. You would get the best answer from someone who has taken more than one review course - a person that could compare courses head-to-head and note the pros and cons.
However, you should also know, people would probably give a biased opinion as well even if they took more than one course. I suggest that the LAST class a person takes (before passing their exam), they would consider the BEST.
I would advise you to decide what's "best" or most important to you when you look at the definitions I gave above. You need to ask that presenter why their program is the "best" according to your criteria.
Be aware though, there is NO WAY anyone can tell you their "passing rate" with 100% accuracy. The reason is, two fold (1) ENA only publishes the "passes" -not the total number of people taking the exam; so if someone does not pass, they may not tell you this information (2) The instructor will have no idea if some people don't even take the exam or not. Many people attend review courses and for various reasons do not take their exam or put it off and thus they aren't useful for accurate stastics.
Hope this helps.
DISCLAIMER: I do a nationwide 2-Day CEN review course and have published CEN review materials.