Look at Alabama, Ohio State etc. They get 5 star players and they dominate.
Yes there are always those under rated that end up playing somewhere else, or those 5 stars like Heaps that bomb.
I would take a 15 5 star players over 12 3 stars and 3 5 stars any day, as the averages are just in your favor. Not to mention those 5 stars usually happen to be quicker, stronger, more athletic overall than a 3 star.