Larry I agree with you about HD vs SD.
I always carry one additional magazine for my primary sidearm. (If I need more than one magazine, I will be carrying a long arm, and the sidearm just moved to secondary position in the batting order, with the BUG to third.)
I disagree with you about a BUG. I don't know about your life, but in my life STUFF HAPPENS. I have been in enough gunfights to know that guns jam, break, get shot, get dropped, get taken away, and sometimes simply black magic stuff happens.
In my life if I am in a firefight it is usually not a good day and bad stuff tends to pile on bad stuff.
Frankly in my life, "STUFF STILL HAPPENS". So I still keep Plan 'B' on standby and carry a BUG.
Because of that, I believe a plan 'B' is always a good idea. I believe that in all things. My daughters say that it is because I am just to negative. I have found having a Plan 'B' has kept me from getting REAL negative during my life.
That is exactly what the BUG is for. I have carried a Shrouded or hammerless 'j' frame for BUG duties since 1967. In Vietnam I carried a M14 for my first 1.5 tours, and a 1911 or Victory model S&W as secondary. In my trouser's cargo pocket there was ALWAYS a S&W model 38 as tertiary. I left the Smith there with a friend when I came home.
By the way I never have had to use my BUG. I had to use the secondary several times in Vietnam, but the tertiary BUG was never needed, thank GOD.
May you never need a Plan 'B'. Good luck.
Fred