What are the advantages and disadvantages of french grips and pistol grips?
Advantages: Its much easier to hold than a french grip, this also means that your point is easier to control (unless youve been fencing for a long time). Your parries or attaque au fer are more physically powerful with pistol grips than french grips and if someone strikes your weapon, theres less chances you'll drop it. Better point control and a better grip on your weapon is advantageous for foil because of the smaller target and priority. However, it can also be helpful in epee if you want to snipe someone on smaller targets. It's also easier to do flicks in both weapons with a pistol grip. Lastly, pistol grips come in more different shapes, so they're slightly more customizable than french grips.
Disadvantages: since the grip forces your hand in one position, it's harder to do funny angles with it (especially for infighting). Some people have to bend their wrist to do an angle when theyre very close to an opponent because otherwise the grip stops anything that is a little too funky.
advantages: The french grip can give you a longer reach if you pommel (hold it further down the grip) which can be a good advantage or make up for shorter arms. This can also mean that your forearm can be "hidden" further away behind your guard than with a pistol grip. This is very good for epe, not so much for foil as there is priority. It also allows you to do funny angles during infighting. Also, some epee fencers like to bend their grips down in weird angles that makes it customizable to fit hold they hold their weapon (and therefore hide their forearm from an opponents point even if they hold their weapon arm higher than they should).
disadvantages: it's really the advantages of pistol grip; it's harder to hold onto your weapon, there is less point control and your parries/attaque au fer are less powerful. It also makes your arm tired much faster (unless you've been fencing french grip for some time).
From what ive seen most foil fencers are gonna use a pistol grip and its about 50/50 for epee. However, of you're usure which one you would like to use, you should try fencing with both for a while and use the one that is the most comfortable and fits your fencing style the most!