Depends how big the deer is and what your chances are of finding an elk. If I knew I was going to be into elk at any time then the deer would really have to be a good one. I suppose it might also make a difference how much time you had to hunt elk. If just the weekend, then you might want to concentrate more on killing an elk, and spending more time deer hunting during the late season. Really there's no one way to answer that question as it depends on too many other factors. Personally I would have to let the deer walk because I have a modern firearm tag for deer, and muzzleloader for elk.