I am convinced that the higher is the bonus the better is the team. It's difficult to get from 8 to 10% but I try to do it every time I play an important game (so, basically, every day !!). It takes me 2 videos to get double bonus from two 10-11% training sessions which involves 10-12 players each. Then, I run 2 more smaller sessions without video. If not, you need to run an extra 2 to reach 10%. Easy to figure out that those 2 videos are much profitable. So, my conclusion is: no hesitation - priority given to videos for double bonus. Much better investment than saving them for resting 15% of a single player.