I am curious to know how a barrel at the bottom of the gun decreases muzzle flip ? Just the different center of gravity and a change in the way the recoil forces work when fired from a lower barrel than one that is at the top ?
A lower bore centerline has less leverage upon the grip frame, when fired.
I haven't had nearly enough coffee to discuss physics, but those are the Cliff Notes.
As cool as the lower barrel is, it requires a more complicated action and thus, higher price tag.
Plus, they're funny looking.
Less muzzle flip is nice, but there are no free lunches.
The decreased muzzle flip results in more of the recoil energy being directed straight into your hand and wrist.
Depending on the gun and chambering, this may not be such a great thing.
In a lightweight .38 or .44 Special, I wouldn't like it.
In a magnum revolver, I wouldn't like it, especially if you shoot actual magnum loads, not the hot Specials that the big ammo companies sell.
For my money, I'll stick with the basic DA revolver design as made by Colt, Charter, Ruger, S&W, etc.