tn24,
Is the younger buck on the left classically shaped for a 2 1/2 in that area? If so, then I would shift towards the buck on the right being 3 1/2. If the buck on the left is small-framed for a 2 1/2 in the area, then I would stick with 2 1/2 for the buck on the right.
Bucks from different geographic regions can look VERY different at different ages. I remember talking with a manager from central FL who was showing my trail-cam pictures of what here would be your basic 4 1/2 year-old. I was shocked when he told me the buck was known to be 7 1/2 years old, and looked it for that area. In addition, I've seen confirmed 3 1/2 year-olds from the far north that most here in TN would say are 5 1/2.