All the years I hunted the southern zone I used various shotgun slug models and took my share of Deer with them, a well placed slug kills as good as anything. Back then it was the law so we used what we could. I can understand sticking with a firearm you are familiar with and have had good results with.
For the last thirty-five years doing all of my Deer hunting in the northern zone I have used various rifles, not because they kill better but for their much more precise shot placement especially at longer ranges. With an accurate rifle you can thread the needle through small openings if need be or make a kill easily out to several hundred yards if the opportunity arises. From my perspective a rifle has performance in spades over the shotgun slugs in almost every situation giving the hunter a better chance at success. If I could have used some of the rifles I own now back in those old open country southern zone hunting days it would have been a massacre.
Al