Commentary reposted by permission of poster "jBirch" from the Fencing.net discussion forum.
Fencing.net

"Here's my take on the issue"

In my opinion, the French is a much better grip for all-round fencing, however, it takes much longer to figure out. One of the things that I hate about the pistol grip is the upward prong that gets in the way of really feeling the opponent's blade through mine an advantage that the French has as well. The French is much more agile at angulation (the pistol grip, by design, makes it harder to angulate extremely) and is better at infighting (again, because of the ability to really angulate it). Pommelling gives you a not insignificant advantage at all levels in epee, however, it is absolutely impossible to flick with it. *grin* (well, not impossible but pretty hard to do it right) It is also easy to knock it out of someone's hand and generally take advantage of when opposed with strength. (the key to the French is to not get opposed with strength). Because of that, in foil, it works well as a beginner tool, gets whalloped as an intermediate tool and then makes an average comeback as an expert tool. In epee, it doesn't get creamed as an intermediate tool.

What I see happen is that a beginning fencer reaches a point where the flick and the strength of a beat/attack start to take precedence in their game. Part of this is because they haven't figured out how to move right and their timing is off, part of it is because they haven't figured out the real precision required to make the french really work and finally, they haven't figured out how to handle flicks and strong beats. So, they get to a point where the french "no longer works" and they switch to the pistol grip. Coaches who are interested in competition encourage the change because their fencers do better with the flick and strong-beats in their arsenal when it comes time to make a choice for the same reason: other students find them hard to counter. So a beginning-intermediate fencer with a pistol grip does better in competition then one with a french grip. In order to be a top-level fencer you need to have been a good beginner/intermediate fencer. See the issue?

When you get to the higher levels, the advantage offered by the flick in certain circumstances and the lack of intermediate training with the French, conspire to give the pistol grip prominance. It's the kind of thing that takes 10 years to figure out properly which means that, almost by definition, you are outside of your athletic peak when you can really take advantage of it. Add to that the lack of precision required to hit the foil target (it's pretty damn big!) and point control/minimal arm target (the real advantage of the french) and you've got a game where the pistol grip gives one a not insignificant mechanical and technical advantage. It's also why older fencers/coaches tend to go back to the French grip when they start to get out of competition.

In epee, where precision, angulation and reach are more important than strength and flickability, you have a place where the pistol grip doesn't have the same advantage over the french even at intermediate levels, so you see it more often at higher levels. Epeeists generally aren't as scared of the flick/strong-beats and have figured them out earlier, so the compelling reason to switch at the beginner/intermediate transition isn't as strong.

Hope this helps.