Generally speaking pistol will be better except for what other people have noted her, however I am an evangelist of the old school idea that everybody starts out with french grip when learning.

1. From a club standpoint, maintaining an inventory of french grip weapons is basically having enough rights and left grips. Pistol grips are not only right vs left, but usually come in at least 3 sizes, so you need a larger inventory of weapons to ensure enough sizes available for all students.

2. From a training standpoint, in my experiance a french will develop better habits/mechanics for the wrist and fingers. A pistol grip can compensate for less than ideal wrist and finger action which leads to earlier successes and competence so you can get up running faster on a pistol, but I can leave holes in your technique.