I had a pair of Korker Metalheads. Loved the light weight but found they weren't great for ankle support. Used the felt soles almost exclusively. The Boa lacing system was just ok. I found it was good for the footbox, but didn't tighten enough higher up the boot to provide support. Went to a pair of Simms Guides (felt) - great support, super comfortable, grippy soles, but very heavy, especially when wet. If you're not doing a lot of walking, these would be a great boot. Just got a pair of Patagonia ultralights for Xmas. Haven't been on the water yet, but walking around the house found them to be very supportive and extremely light.
Being on the far side of 50 myself, I would suggest getting him a decent collapsible wading staff as well. He'll appreciate it - believe me.