"I haven't found a clear choice or a rule for selecting the best. The larger file is often better, but sometimes it appears to just be a waste of space. Also I can't tell the file size until I start downloading. I'd like to avoid downloading every pair of videos and having to compare them one by one."
i have the same questions, but at this moment i just watching the videos online without downloading at all. it's just a bonuses - a now i don't want asking the team for their quality, etc. much more important a bug fixes and usability aspects of the client application (keyboard, player, filters, frames, etc, etc, etc).