A note about the finger on the trigger guard style. It's interesting to note that up until Rob Leatham and Brian Enos came along, this was the predominant style in competition shooting circles. You'll see a lot of guns from that era with flat front trigger guards, and checkering on the trigger guards because of this. Leatham and Enos decided to try something different, and not put their support hand index finger on the trigger guard like that, because they felt it was negatively influencing the tracking of the gun. They felt there was more of a tendency to push the muzzle left or right with the index finger out there. Once they changed their style and started getting the phenomenal results they did, all the other competitors kinda followed along and changed their grip as well. Now, you'll be hard pressed to find anyone in USPSA/IDPA/IPSC who uses the finger-on-the-trigger-guard grip.
Now shooting big bore revolvers in single action is a whole different ballgame. I still don't do it unless I'm shooting something that is exceptionally muzzle heavy, or a scoped revolver, because I feel like it adds a bit more support out front. But I shoot all my semi autos and other revolvers with the same, no finger on the trigger guard style, so that's what feels comfortable and consistent to me. I did notice more of a tendency to have horizontal stringing of shots when shooting with the finger on the trigger guard, too.