Forgive me if I'm wrong, but I think a decal is an image with an alpha channel (on a plane) applied in the editor (or in game via script or the engine itself), but not actually mapped to an object, and a texture is simply mapped to a mesh. The video texture would allow for many other options, like a television, movie screen, or a monitor that feeds from a remote camera (provided we get additional cameras; think security system). I'm sure there are many other possibilities (Predator?).
MAME Cab PC: i7 4770@3.4Ghz (passmark 9945), 12GB RAM, Win 8.1/64, GeForce GTX645 (passmark 1898); Shiny new laptop: i7 4800MQ@2.7Ghz (passmark 8586), 16GB RAM, Win 8.1/64, GeForce GTX870M (passmark 3598); Old laptop: i5@2.3Ghz, 8GB RAM, Win 7/64, Intel 3000 graphics