The 28 will do "Anything" the 20 will do!!!
Like Larry I greatly question this statement, but let's go a little further,. If it be true, we can likewise say a 20 will do anything a 16 will etc all the way up to an 8 doing anything a 4 will do, taking it one step at a time. bottom line is in effact one is saying 3/4oz of shot will do anything 4oz from a 4" 4 gauge will do. Do you Absolutely & Honestly believe that???
If adding shot to the charge at any level makes no difference then no amount can be added to make a difference. Each step may make only a small difference, but its there or an accumalation would have no effect. The best word I can come up with to describe the statement "It will do anything a 20 will do" is Ludicrus.
The first shotgun I ever shot in my life was a little 28ga H&R small frame single which weighed just a couple oz's over 4lbs. I will always have a soft spot in my heart for the 28. never-the-less I recognise it for what it is, a nice little gauge for the uplands, & while I have no experience with wild pheasants it certainly would not be my pick should I ever have an opportunity to hunt them.