"Can you articulate to a jury how someone attempting to draw a gun at you poses an immediate, potentially lethal threat? Can you articulate that it doesn't matter whether the gun they're trying to draw is on their belt or yours?
As I understand the general legal principle (and the actual statute here in Texas), the first question is the only real issue of concern in a legal defense of a homicide*. If you can demonstrate that someone(s) present a lethal threat to you (or another), the law doesn't care what legal means you select to defeat said lethal threat with. You should be aware that "legal means" would be any object you use to kill the individual(s) lethally threatening you. Local ordinances always apply, of course, so the prohibited weapon choice list varies wildly, but as a general principle of self-defense, if you are at risk of losing your life, you can use whatever you have to to not be non-judicially killed (which pretty much rules out nukes, chemical weapons or that seriously irritating toddler whose oblivious mother will not shut up, to beat the guy to death with in just about any non-ISIS jurisdiction around). Basically, if you are lethally threatened, you can shoot the person making the threat no matter what weapon s/he threatens your life with (to include your own gun).
Similarly, the law pretty much doesn't care what you use if you should prove to be the one offering the lethal threat, so the second question ought to be sorta irrelevant. Prosecuting attorneys being what they are, you better hope your attorney is well versed in the applicable laws. I recommend these guys without reservation. You quasi-ferinners can go with this option until you can get here.
*For the hoi polloi, the term of law "self defense" is an explicit admission that you have committed homocide. The only remaining issue thereafter is whether or not you were justified in doing so, and the cops don't get to make that call. Should you ever find yourself in the vicinity of a freshly deceased example of the genus homo sapiens, make absolutely certain that the two words never to exit you mouth at any point thereafter are "self" and "defense". The way that works is, your lawyer presents evidence of the justifiable nature of your actions to the court, thereby leading the jurist-in-residence to rule "justifiable homocide by reason of self defense". Self defense is a legal ruling by a judge, not a statement to the police.