Depends on what you're doing with it mainly. I really like my pyrex baking dish because it's safe to use on the burners so I can cook something in the oven and then deglaze it on the stove, which I don't think the stoneware can do.
I'm not much of a baker (I don't eat grains and much of what would traditionally be baked or broiled I cook in the sous vide machine and sear on the stove) but my current bakeware consists of a loaf-sized pyrex, a shallow baking pyrex, a cookie sheet and a half pan. They all have their uses.
I've never seen a pyrex dish in the shape of the Corningware casserole you linked. That's a great shape for stuff like shepherd's pie. I don't own anything that I could bake a proper one in. Curved sides won't let you cook a proper pastry-encrusted dish. Those stoneware dishes are also handy because you can use them as serving vessels. And with a little creative lubing you can bake cakes in them.
Are you planning on just baking with them or do you care about being able to use them on the stove top or microwave? Most of my cooking implement purchases are based on recipes I'd like to try. I'd recommend basing your next purchase on what you want to cook, then in true arfcom fashion, eventually buying both