When one's life is on the line, it is apt to happen at night. There's nothing positive to gain by shooting a flamethrower round. It won't impress the person attacking you, for all he's thinking about is surviving too. You'll just blind yourself so your eyes can't adjust for a while . . . and that's never good to hear, or feel your attackers bullets while you can't see where they are or focus on your sights.
Ultimate velocity is, in itself, not much to desire either when it is life or death. I want a round which will allow me to control the firearm as fast as possible for accurate, follow up shots. Truly, you'll never know how the the recoil can twist your firearm out of its normal place in your grip until you are shooting fast strings against the clock and discover you suddenly can't hit the target because the gun changed a bit in your hand. Yes, the gun HAS to fit you properly . . . when firing a lot of rounds very fast.
Go to some serious handgun matches and watch who wins. Nothing beats speed and accuracy, and high velocity and muzzle flash contribute to neither. Certain rounds have a reputation for being able to get the job done extremely well with lower, more manageable type recoil characteristics. .45ACP is one of the very, very best in this regard.
I handgun hunt (deer and hogs) with a 6" S&W Model 29 .44 Magnum. My round is the 300 gn. Federal Castcore . . . but I wouldn't use it in a bowling pin match or a steel match.
10mm proved not best for most shooters in gunfights, it was too hot until loaded down to velocities of the .40S&W. I do know one S. Carolina trooper, a big man, who carried a Glock 20 on patrol and in LEO matches back "in the day," but that's very, very rare. I only could wonder how much faster and more accurate he'd have been with a Model 21 (same grip frame in .45 ACP).
Just food for thought!