I raised this question b/c of an article I read, which surprised me by a bit by casting muzzle flash as a positive. I'm not sure about the motives of the author - it seems to be part of a larger "sales pitch" for Charter Arms revolvers - but its well written and sorta persuasive for a newbie like me. Thanks to those who have argued the opposite position - I'm not planning on LOOKING for muzzle flash in ammo choice, I just wondered if I should be avoiding it in a SD round. The consensus seems to be that I should (avoid it). If interested, here is the relevant part from the article:
"Handgun muzzle flash (regardless of type of handgun) can actually work to your advantage. If you are under assault it is pretty obvious the attacker knows where you are; well no duh! If you must fire to protect your life, muzzle flash giving away your position is hardly a concern.
When a handgun is fired at an attacker close in (especially at night or in reduced light conditions) the attacker facing the muzzle gets all of the flash, every glorious bright bit of it. This can cause some temporary blinding (flash-bulb effect) as well as a tremendous psychological effect even if not struck by the bullet. In addition, if the attacker is very close and if the defender misses (it happens much more than you might think at ranges under 10 feet with any gun—just watch the cop shows where both cops and bad guys spray bullets all over) the attacker gets massive noise, flash, heat, and certainly some hot powder particles all of which may diminish the attack somewhat and that may be all the time you need for follow up shots.
However, the defending shooter will only see some flash over the top of the revolver, not the whole ball of bright light the attacker gets. Another advantage in dark or low light conditions is the flash silhouettes the defender’s sights. This can help the defender adjust quickly for a second shot (experienced and practiced shooters can routinely take advantage of this, even in total darkness). This brief instant of flash can be even be utilized by less-experienced shooters also; they just need to be made aware of it and how it can help them.
We feel (regardless of firearm) that a bright muzzle flash is an advantage in nearly all self-defense situations that goes to the defender and is a distinct disadvantage to the attacker—and for what it is worth, shorter barrels deliver more flash."
http://www.ammoland.com/2010/02/03/revolvers-the-advantages-as-a-self-defense-gun/