Times change... When I was in patrol the rifle was in the trunk and the shotgun was in the rack up front, so it was the immediate "go to" and the rifle was used when I had time to grab it. I almost always favored the rifle, but as I stated, there is a place for "the boomer".
Now, with many of our units having both up front, I'd be more likely to grab the rifle over the shotgun, but for those certain situations (barriers, animals, etc.), I'd absolutely go with the shotgun. So yea... I'd take one or the other depending on circumstances, but it would mostly be the rifle.