OC, Tasers and Guarian Angles have one big advantage: You don't have to think twice. If you misjudged the situation, you apologize, give the - good - buy money or buy him a drink and that can be it. Try that with a handgun
So, I sometimes carry OC (with my 9x19mm) eg when running in the woods. If a dog comes to close, I don't need to think to long, if it's to close, I spray it. No blast, no casing lying somewhere, no dead dog, no mad owner.
And if the dog tries to kill me, I can still shoot it.
Same applies to unclear situations. If I feel that pulling the gun might be to much and I could regret it - I can use OC as a first defense. Switching to the gun wouldn't take long. However, I don't advocate using OC in a clear lethal threat situation. If the leathal threat is clear, the answer is clear: The fastest and most reliable way awailiable to stop the threat, and in my case that mostly is a 9x19mm Glock or a .223 rifle.
Have a nice weekend,