Take a look at this:
Chris Costa (America's best sniper)
IPSC world champion
US Army Action Shooting Team
Smith & Wesson Ad
You see this:
And not this:
If 'straight thumbs' is good enough for the world's best in pistol craft then it's good enough for me.
I got into a spitting match over a post like this on another forum. People don't like being 'advised' they are doing it wrong. Don't do what I say, look above. Thumbs forward is the hot ticket, but it's not new. I was taught it over 20 years ago at The Tactical Defense Institute in Ohio. If you don't like it that's cool. Just realize our US Armed Forces teach it, Gunsite and Thunder Ranch teach it, LEOs and SWAT use it, and the best competitors in the world use it. Not one uses 'crossed thumbs'. Why? Because when you cross thumbs your left (or right) palm cups and you don't have as much meat on the grip.
The problem with thumb-over-thumb is that under stress it’s just all too easy, since you’re basically holding the gun wrapped in your fists, to begin muscling it, generating forces on the gun causing it to do a hula dance in recoil. Also, because wrapping the left thumb over the right opens up a gap between the heel and thumb of the left hand and the gun butt, the piece can twist in your hands under recoil, thus your group size explodes at speed. All those above have figured that out.
Just passing along info...oh, and 'straight thumbs' is not a revolver thing. That's a different animal. I bow out on that topic.
...and I respect all of you. Do as you wish. 'Straight thumbs' isn't for everyone but it's worth a look.
Here are some articles on the subject: