I can see this is an older thread but I'd like to respond anyway just in case it might help someone out.Brian has the background info pretty much on track but The Asi and VOX sensors are backwards. The Asi is the less expensive and each are able to be formatted to the smaller size units. Raytheon technology or BST is what he refers to but is not microbolometer technology.As far as the difference in pictures goes I would have to disagree if we are talking about units available at the time this thread began, However. The constant improvements in software and electronics have certainly had an impact on picture quality across the board.One last thing, BST units like those refered to as larger cameras, are no longer manufactured for the fire service. Hope this helps.