I am of the opinion that factory dimensions are the best dimensions for function in gas guns. A lot of money was spent analyzing the “best” tolerances and clearances for maximum function reliability. So why go larger? Why is larger better than factory?
I don't think anybody is saying larger is better. What we are saying is why waste money on a small base die if the normal die works fine. The OP won't know until he tries. You also say that he will have a problem once he starts using range pickup cases. I'm curious why that is. All the 223 brass I have is range pickup. I have never bought new brass or factory 223 ammo. The hardest I have shot my AR is at a rattle battle match at the club I belong to. The rattle battle is a match where you shoot as many rounds as you can in 60 seconds prone, then as many in 60 seconds kneeling and then as many in 60 seconds standing. I use 30 round mags and will usually do a mag change in that 60 seconds. I have never had a feed or extraction issue shooting one of those matches. Is that hard enough to make a standard die fail to where you would need a small base die and if so then why is my Lee FL sizer working just fine.