Shot placement matters, obviously, (in other words getting hit in the chest or head is likely lethal versus being hit on an extremity), so also consider getting hit with a BB traveling at 900fps, or a cannon ball traveling at 100fps.
Your last premise fails the sniff test...
Which entirely destroys the straw man argument you've tossed out into the wind.
A derringer, especially a high caliber one is NOT Practical and I imagine you know that. Or would if you'd ever fired a high caliber derringer. You've got to get close enough to actually hit something with it 1st and if using a 45-70 (does a 45-70 derringer even exist) unless the shooter were superman they'd have a sprained or broken wrist.
You're arguing MoBoost just for the sake of arguing - which can be a hoot I will admit. I've been know to do that too.
But it's getting us no where and is just wasting bandwidth. You go light and fast; I'll go heavy and slow. Hopefully neither of us will ever have to test our judgement re: what works best.