ORIGINAL: Power
Sure, you can ID the animal with your binos but when you pull up your rifle you need to find that spike again and be DANG SURE before you pull that trigger.
I ran into a similar situation on one of my hunts not long ago.I spotted a group of elk with my binoculars and identified the animal that I would shoot.However when I put down my binoculars and raised the rifle,I discovered that the elk in my scope didn't look right.Because I was using a very bright scope I was able to pick out the right elk in the scope and I then realized that the bull that I wanted had moved a couple of steps.I then shot the correct bull.I should mention that it was at first legal light and it was overcast so it was quite dark.A not so bright scope would not likelyhave allowed me to properly identify the right bull and I may have shot the wrong one not realizing that the bull that I wanted had moved.