These things are subjective, of course, and I barbri is the only bar prep course I have ever taken, but I found barbri to be completely helpful and an essential part (heck, the only part) of my bar exam preparation - both times. Maybe other courses are better, and I have no point of comparison, but I certainly thought barbri was good. Very good - certainly far better than most CLE I have ever done.
On a more objective level, however, I might suggest that barbri is the best simply because it is the most used. There is a certain statistical safety in cohorts. Most people pass the bar exam, and most people use barbri to prepare. This will tend to pull you towards the modal score, which is a passing score.