it's important how many fins a fan has, but the shape of the fins and their rotational speed has just as much, if not more, impact on the fans overall quality then the number of fins.
All things being equal, a fan with more fins will perform better than a fan with fewer fins- but only up to a point. Past there, the fins will interfere with each other's airflow and screw things up. More importantly, 'all things being equal never' happens.
It's best to look at voltage and CFM numbers of a fan instead of just buying a fan cuz it has lots of fins, that's what I do.