Adobe AIR for Video Wall project - the right tool?

Pros of the Adobe route would be a little more control and reliability. You can easily go fullscreen, preload other videos easily in the background and display them on the hardware GPU decoded StageVideo (with the right video card, almost all of them at this point). Twitter feed loading would have some robust error handling to assure it goes smoothly but if you need offline capability you'll need some canned material for the feeds in that situation.

HTML can go fullscreen but the caveat would be drawing your twitter feed over the video at that point. Because it's fullscreen I don't believe you can have your text over it from a <video> element but you'd need to use <canvas>'s fullscreen and actually mux the text into the video.

The long haul of Adobe's roadmap clearly states video and games are the future of FP and AIR. I've done tons of kiosks in Flash and AIR, many of which just act as a video wall, attracting people to very large screens. I've had nothing but success doing this. I'd only even approach HTML5 if you have some reason to desire to put this on the web, and even then, Flash is still fine in that situation too.