I would mix the two. Not sure about supplementing with glucosemine. Hopefully someone with a large breed will give input on that.
The TOTW foods do have Vit E added and have omega 3's and 6, which is good for the joints, heart, and skin. Not sure if it is high enough to act as an antiinflammatory.
I think you and your dogs will be happy with the change. I know I like it and my dogs LOVE it. They love it so much that I use the kibble as treats for good behavor and/or training.