Most of us have a rifle that is perfect for the terain, conditions and the game we are after, then we have another rifle that is better suited to different game or condition but will work for the primary animal we are hunting.
When elk hunting, that new belted or not mag you bought in dull stainless with a kevlar stock and super optics to be able and hit a royal from 100 to 500 yards is the perfect rifle, but that trusted old rifle you have been shooting deer with for years with open sights or a lower powered scope will work as well. Since you have the rifle why not bring it. When I first went to Mt huntng for elk, the scope i had on my rifle was huge and we ended up pushing through a dense woods I wished I had my NC Deer rifle with me. Since then I bring a second rifle that would be a brush rifle, as well as act as a main gun if my rifle is damaged. If you own it and it will not be a burden to bring, why not bring it?