I don't subscribe to the single gun mindset. Sights are sights. Trigger control is trigger control. Gun has a safety? No problem. Gun has no safety? No problem. At minimum, I can shoot any gun with combat accuracy.
I go with single gun because...
As you say, sights are sights, trigger control is trigger control, etc. You are absolutely right.
I go with one gun not because of the gun but
because of the carry.
In a high stress situation, like it would be if having to use your gun for self defense, I do not want to have to hesitate for even a single second while I figure out where the gun is...IWB right forward cant at 4 o'clock for the big gun, pocket holster in right front pocket for the itty bitty revolver, shoulder rig for this gun, ankle holster for that one, and a waterproof derringer stuffed in my speedo when I go to the beach...


If I ever have to pull I want to reach for it in in o
ne place and know what's there, exactly where "there" is, and how its carried (vertical, forward cant, etc).
Sure, I could practice all of that at the range, or even dry firing exercises, and do it perfectly, but...
The split second it takes to remember which piece of training for which gun to access mentally is still there and in a high stress situation we all will devolve to our training.
... I also believe that anyone who drives a car should learn to drive using a manual transmission...
Cars can have automatic transmissions if the owner wants, but every puckup should come with a manual only...
< end premature old-guy rant>
Old farts rule!