I love chard - just regular Swiss chard. I prefer the green kind (Fordhook Giant is the one I generally grow). I think it's better than spinach. I also think beet greens are better than spinach. So I'm not really stuck for a spinach substitute. Chard has always grown VERY well for me, never any problems with it.
But I'll definitely also try Good King Henry: who could resist growing a plant with a name like that? :) Not me.
Pat