Honestly, from what I've seen, either will do the trick. I've had bang flops from both. But, sometimes an animal just dies harder with no apparent reason. I mostly shoot 300 gn hardcast out of a .454, loaded to about 1700 fps. Should be enough to put down a rhino. I know it will penetrate about 10" of live green pine. I shot a smallish doe a few years back, hitting her on the point of the shoulder. She ran off about 40 yards and laid down, but with her head up and alert. Put another in her chest. She tried to get back up, so I put one in her neck. She was still writhing a bit, so another to the neck. That's 1200 gns of lead in a 110 pound doe. When dressing her out, I found that the first shot broke her shoulder, took out the lungs and exited through an offside rib. Second shot destroyed the liver. I still don't know what kept her going. I dropped a buck of about 150 pounds with that same load. Facing me at 40 yards, the bullet entered the chest just below the neck, raked 3 ribs, breaking them, destroyed the lungs and entered the right ham, stopping about 1 inch shy of exiting the rear. All in all, over 4 feet of penetration. He dropped like he was poleaxed. You just never know.