When I developed the LBT handgun bullets most of what I 'knew' about revolvers loads was that the most powerful wasn't powerful enough. Consequently, the bullets I developed have a higher power potential than any in the world, and I seriously doubt that anyone can develop cast bullets that will wring more power from a gun, and deliver it more effectively on game.
I've been way deep into flinch country, and the only way I overcame it was shooting partly filled cylinders using loads that didn't hurt. When the hammer falls on an empty case and the gun takes a nasty nosedive from your flinch one tends to get hold of things fairly quick.
But I learned that my WFN's don't have to be driven to anything near full power to kill when I loaded some 240 gr WFN's at 1200 fps for a 44 mag marlin with intentions that my wife could use them to trim the heads off grouse. She never did use it, but the last day of deer season that year, and I hadn't had time to go out even once, I picked that little gun up about a half hour before dark and went down into the woods on the back of our place. A half mile from the house I took the eye out of a little buck at about 100 yards. In thick brush, with his head all that was visable. He dropped so fast I didn't know he went down. So I listened and watched for any movement, then saw him again about a little ways from where he was the first time. This time his ribcage was in sight and I thought. Well I can hit THAT! He dropped instantly at the shot, and I saw him go down this time. When I got up to him I found them both. Of coarse a 22 long rifle would have killed the first one, but it wouldn't have crushed his skull like this thing did, which means if the brain is missed by an inch or two it isn't likely the deer will be wounded and get away. The the second rib shot deer is what impressed me most. Hit at a steep quartering angle the bullet traveled 20 inches and left with a one inch exit hole, which was the size it made all the way through. I killed three more deer with the same load, one at about 30 yards, two more at about 100 yards, and all dropped in their tracks. I made sure to put all the other shots into the ribcage so nerve hits wouldn't be in influence, and all were instant kills.
I don't make a habit of recommending loads slower than 1200 fps with the 44 WFN, but get quite a few reports of shooters who shoot 44''s and 45's at speeds down to 800 fps, who all claim excellent results on deer.
Eskie John sums up the issue real well. The first thing in importance is a load that one can control with precision. Power is second as long as ENOUGH is a primary concern. People like him and myself can get along real well with little power, but many deer hunters can hardly get out of sight of another hunter, and have far less experiance, or none with deer hunting. So I recommend a power level and bullet that I feel reasonably sure will anchor most deer in their tracks, or let them move only a few feet. The same works for elk and moose, etc.