It would go boom for sure. You'd probably have to do some side by side paper punchin shootin to see what is more accurate. I use FF (25 grains) all of the time in my 44 Colt loadings for my three Colt conversion revolvers. Used to use FFF but Fox Creek Kid pointed out some years back that he had 'a more harmonious outcome' using FF vs FFF in the 44's. Had to do with the pressure curve/spike of the speed of the faster burning FFF, less with FF. The increased volume of powder in the 44 cases vs a smaller caliber had alot to do with it if I recall right. Accuracy wise, I've never noticed any difference. Talking my use of Goex powder by the way. Have used around 27 grains (FF) in 44 Special cases but I don't load/shoot much black in the 44 Sps.
In my 38 Special chambered Colt Conversion, all I've ever used is FFF (19 grains), have never tried FF. Supposedly the smaller volume of powder used in a smaller calibered revolver cartridge isn't as noticeable as far as the pressure curve as it is with larger ones such as the 44's. Hopefully someone on the forum has used FF in a 38 size shooter that can give ya more insight.