Screens have a very limited range of brightness. More importantly, they only project a picture in one direction, so, if you can move laterally, you'll notice that it's a flat picture.

If metamaterials can alleviate any of that to some degree, they could make a form of invisibility cloak covering large objects practical.

Agree, both screens and metamaterials for this application have their pros and cons. Manufacturing metamaterials at a large scale is an area I'm looking into next!