Some people will say an external safety is a determinant if your carry gun has one. Just another step to remember to do in a panic situation. That it takes too long to turn it off., if you remember to do it.
For me, I prefer a carry gun with an external safety. I like thumb safeties. For my competition guns, it doesn't matter. I am currently shooting a Para Hi Cap 1911 with a thumb safety. I am used to thumb safeties. When I shoot my 5" Pro w/o a thumb safety, I am always trying to sweep it off. I laugh at myself and carry on.
When I put my 9c in my purse to use the restroom, I feel better with that extra layer of security. I have been complemented on my safe gun handling, so it is not like I am not safe when handling my gun. But in my book, being too safe is impossible.