RE: To stop a deer in its tracks
Like stated previously you can hit them a bit farther forward and higher and break them down. I hit my buck this year high and broke his back. I wasn't far enough forward to kill him right off so I ended up walking up and putting him down.
Shotgun slugs, at least the sabot I use, have plenty of knockdown power under 150 yards. I would think the traditional style slug would have more at closer ranges but loose some out farther (plus the acuracy goes away)
I'm like you though I plan for a double lung shot. I bowhunt and have trained myself this way. Hard to break that habit. On my buck I unintetionaly hit him a bit high but it did prove the point to me that I need to aim different with a gun.