I initially shot with my weakhand index finger on the front of the trigger guard. I was using a weaver stance and I guess it helped "pull" the gun into the strong hand. After I started competing, my grip and stance evolved to an under the trigger guard grip and a modern Isosceles stance (discussed elsewhere on the forum). There are some definite advantages to me, the extra gripping strenth mentioned as well as the ability to cam the wrist of the weak arm which makes the wrist joint stronger, I think. Most of the better shooters in USPSA/IPSC shoot with this grip, demonstrated here by Todd Jarrett.
However, there are a few notable exceptions, the most notable of which is Eric Grauffel. Eric is a French shooter that has won the last 4 World Shoots (held every three years) in Open division. He seldom loses anything he shoots, including when he picks up a Standard or Limited division gun, so it is not just because he shoots an Open gun with a comp that doesn't have as much recoil that the grip works for him. If you have some time, it is worth going to his website,http://ericgrauffel.com/, and looking under "Eric's Info" and then checking out the "Internet Videos". I recently saw the CCI Primers commercial on TV, and the El Presidente video is a classic, though it is about 10 years old or so. The weakhand index finger on the trigger guard grip obviously works for him. My suggestion would be to try it both ways and see what you prefer. Here are a couple photos of Eric with his grip:
However, there are a few notable exceptions, the most notable of which is Eric Grauffel. Eric is a French shooter that has won the last 4 World Shoots (held every three years) in Open division. He seldom loses anything he shoots, including when he picks up a Standard or Limited division gun, so it is not just because he shoots an Open gun with a comp that doesn't have as much recoil that the grip works for him. If you have some time, it is worth going to his website,http://ericgrauffel.com/, and looking under "Eric's Info" and then checking out the "Internet Videos". I recently saw the CCI Primers commercial on TV, and the El Presidente video is a classic, though it is about 10 years old or so. The weakhand index finger on the trigger guard grip obviously works for him. My suggestion would be to try it both ways and see what you prefer. Here are a couple photos of Eric with his grip:

