IMO neither buck more than 3.5 years based on the bottom picture.
Thats what I was thinking. I even saw the other buck on the hoof last weekend and couldn't nail it down. We're going after 5.5yr old+.
Look at his rear end, compared to front. As a deer get past prime the rear shrinks compared to front. Lot of other indicators, scared knees, short appearance leg wise, loose skin, chest width, etc
High brow is a min 5.5, I'd call him 6.5, because I bet he swells way up here shortly and it will be more apparent.