EDIT: The title should be: 3 extension vs 4 extension... does it really matter anymore?
With todays modern CF tripods, with sophisticated quick locks, does having an extra joint really effect performance?
Can someone point to a study that has been done anywhere that tests this theory?
It is my assumption, that it no longer matters with respect to stability. The only place were it might have an effect, is in the fact that the last extension would be a little smaller then the same tripod with 3 legs.
But I would suspect that a 4 extension tripod, where the last leg is as wide or wider then a 3 extension tripod, will be as stable.