I only collect vintage so I am usually buying the item complete. Good stills and promos can be found online. Identifying them is a whole other discussion.
Wow, that's an amazing piece. You can definitely see the difference between them. I love the vintage style style pictures, but as you say with the copy, the contrast is way off. Still an amazing piece regardless!
Screencaps are generally a bad idea for a number of reasons, and are almost certainly a dead end for 11x14s or larger. The exception would be if the video source was high quality HD and in 60 fps. Even then, it's probably better to look for still photos.