I wish there waas a way to measure how many birds (waterfowl as well as upland birds) have been hit hard by steel but were not recovered by the shooter. That's the worst "crime" of all.
I do not know how great a shot you are, but I can tell you this, I hunted both upland and waterfowl for many years with lead. I have seen birds bagged and birds crippled and lost with both. Lead shot is not some sort of magic death ray.
Last fall, in Iowa, during the first three days of the season, I bagged 9 pheasants with 10 shots. The first day, I shot my limit with 16 gauge #6 bismuth. The next two days, I shot steel. I use handloads of #4 steel in the right barrel and #3 steel in the left barrel. I killed 5 birds with #4 steel and one bird with #3 steel. I had missed one shot.
I continued to hunt the rest of the season in both Iowa and Minnesota and never lost a crippled pheasant.
There has been a persistent myth among some hunters that originated in the late 80s or early 90s that steel shot cripples more birds than it bags.
Now, regarding your wish, wish no more.
There exists a study that did compare lead and steel on birds and measured wounded vs bagged birds.
You can read it right here:
I do agree that lead is ballisically superior to steel and even bismuth. However, all three types of shot will cripple birds if you shoot at them too far away or through one wing.
The problem with lead shot is that it continues to kill and cripple birds and mammals long after its terminal velocity reaches zero. That is why nontoxic shot is mandated in some locations.
I know of people who feel that lead shot is so superior to nontoxic shot that they cheat when hunting WPAs and WMAs where nontoxic shot is required.
I am glad to read in your post that you do not do that.
For years, I too used lead where it was legal and steel/bismuth where it was not. I too felt that I was less effective with nontoxic shot than I was with lead. Then I stopped using lead and my loss rate has declined considerably. I definitely do not take as long shots as I used to and I do not have to be concerned that I have the wrong shot in my possession when hunting public lands.