IMHO variety is better.
Chickens love the cover they can get from brambles - so either raspberries/blackberries or maybe some rugged roses like rugosa - they could supply leaves for the goats and berries for the
chickens not to mention shade and cover. You'd have to
fence the goats away from the actual plants, tho or they'd destroy them, but you could set it up so the goats keep them pruned to a nice hedge. I like
cattle panels because the chickens can go through them but the goats can't. But they can stick their heads through and reach about a foot in, so keep that in mind if you go that route.
My chickens also really benefitted from mulberry and black cherry trees. I'm noticing how much more I have to
feed them now that we don't have those trees (new home).
Clover would probably grow around the comfrey, and if you're really enterprising you could broadcast some sunflower seeds, corn and grains like barley, wheat, oats, depending on the time of year. They all make for good grazing and if they manage to make seedheads that's even more food. Black eyed peas are another possibility - easy to grow and make good feed. If you don't care if some of the comfrey gets shaded out then you could plant some winter squash or pumpkins among them. The seeds are good dewormers, and both chickens and goats will eat the squash (especially if you cook it for them, but mine are kind of spoiled!)