I believe follow up speeds for defensive purposes is greatly over rated.
I suppose this depends on how you shoot. I shoot in "bursts", so, follow up speed is important, and maintaining control of the gun in rapid fire is as well.
Im not really a "games" person, but I do believe that all things should be tried, and proved good or bad, for you anyway. As Bruce Lee always used to say, take whats useful to you from everything you try, and make it yours.
I was a staunch thumbs down and locked shooter for a long time. Once I gave thumbs forward a try, and got comfortable with it, its advantages quickly became apparent.
All those years shooting thumbs down, still have that ingrained hold necessary, when the weak hand is removed, and you are shooting one handed. So some things move on, and others remain.
A specific grip isnt necessarily the only grip, nor should you lock yourself into one. Slight modifications are usually necessary, especially if things are fluid and you are moving. Certain grips do work better than others, depending on the circumstances.
Having tried, used, and knowing them all, and knowing when what works best, fluidly, without having to think about it, is really whats to be strived for, dont you think?
Once you start to move, and deal with targets on the flanks as you go, youre likely going to find that you wont be able to use your normal "static" grip at all.
Assuming a right handed shooter, targets to the right, are basically going to be addressed one handed, as its very difficult to maintain a two handed grip.
Targets to the left, and I think you will see yourself sliding into a form of Weaver as you go.
Theres a lot to be said for being well versed in many things, flexible and adaptable.