SLUG. YOU WILL HIT THE ANIMAL, JUST AS EASILY WITH BOTH IF COMFORTABLE WITH THE SHOTGUN. WITH SLUG YOU CAN SHOOT FROM FARTHER AWAY IF NEED BE. HERE IS THE DESCIDING FACTOR, A SLUG WILL PUT A CLEAN HOLE FROM ONE END OF THE ANIMAL AND OUT THE OTHER. THE HOLE WILL BE LARGE ENOUGH THAT IT SHOULD BLEED QUICK AND ALLOW FOR EASY TRACKING IF IT DOES RUN ( BUT IT WON'T GO FAR ). THE MEAT WON'T SWELL TO LOOSE THE BLOOD TRAIL. THE IDEA OF 00 IS THAT IT IS EASIER TO HIT A VITAL, BUT ALL THE ENTRY HOLES CLOSE QUICK FROM THE SWELLING OF THE FLESH, PLUS EXIT HOLES ARE MINIMAL. LIKE MOST OTHER OPINIONS, SLUG, SLUG, SLUG. I'VE NEVER LOST A DEER WITH A SLUG. PLUS WITH A SHOTGUN, IT IS MY TYPE OF HUNTING, UP CLOSE AND PERSONAL.