Pointintg dogs or flushers? Preserve birds or wild? Windy or still conditions? Early season or late?
I probably over-complicate it but once I started paying attention to the conditions and changing chokes I was putting more birds in the bag. I only shoot 12ga. Early season I shoot 6s through IC and Mod.
When it gets to be late season, the wind is blowing non-stop, the birds are heavily feathered, and my dogs are flushing birds at 30 or 40 yards I use M/F and 6 in the bottom barrel, 4s in the top.
I used to go with M/F in the early season and I think I was over-choked. Experiment and see what works for you. And pattern the gun and shells you plan to be using. Then you know for sure what's happening at each distance with the different chokes.
Chokes and shot size debates will keep manufacturers and internet forums in business as long as there are pheasant to be hunted.