I'll admit I'm just befuddled with recent choices (and I very much doubt we're alone in this).
One would think that for movie-only of a flik less than 4.3 Gb to start with that Constant or Variable methods would be a moot point. [I'd like that confirmed(?)]
As for movies (again, I have a movie-only preference...) that are greater than about 6 Gb., one would think Constant the way to go (more so if even larger and/or having less 'action' scenes).
But deciding which for movies between 4.3 and 6 Gb--does one favor Variable for movies with lots of scene changes/action/water?
If developers were a bit more forthcoming about 'intents and methodology', methinks we wouldn't have so much 'head scratching', ...not that I want them to tip-their-hand to competitors.
I can't really guess at this point what one-clicker can produce (on average) the best movie-only duplicates. I am inclined to think it's currently D2O--if used properly. But I need better guidelines for Constant/Variable. Cost of a program(s) is meaningless compared to investments of time/media...but Quality is a very slippery target to assess and/or implement for average users. We need more info and pointers from those who design the tools, and really understand the mechanics of the code and the intents behind it's updates.