Roy:
I use #5 shot on Pheasant, and it kills them dead out to 30+ yds. with my 12 gauge. I shoot a 2 3/4 Dram load, ( 76 grains 2Fg) with a 1 1/4 oz. load of shot. I have not killed a pheasant yet with plated shot, so I can't tell you if they make a difference. I suspect the difference would be seen more easily if you are using #6 shot, which is a common choice of shot. I moved up to #5 after reading about Commercial Duck Hunters on the Illinois River in the 1870s and '80s, in a reprint of an article from those days in The American Rifleman, about 15 years ago. The original article had been printed in a predecessor magazine of the NRA, but I have forgotten the title of that earlier magazine.
I also talked a a couple of friends who have killed more pheasants than I can possibly kill the rest of my life, and both concurred that #5 shot was the choice to anchor a bird. Both liked how the shot patterned in most guns, too. And both encouraged me to go the extra distance to find the shot size and buy a couple of bags. I found a distributor in Bloomington, Illinois that had some of the shot, and bought 2 bags.
I have used the loads shooting Annie Oakleys at trap ranges, to reach out and smack those long range clay targets with my full choke trap gun. Works like a charm. Starbursts, when I do my part.
I have a bottle of plated shot from Ballistic's products to try in my ML shotgun. Again, it will only be used for hunting, and to check the patterns before I go hunting. I do intend to try it in my 20 ga. fowler, too.