The difference between 70% quality and 74% quality?
The 74% file will create a larger file when 70% quality is all you actually seek. 74% quality takes longer to upload than 70%. It's a guessing game as to where the slider has been placed.
A HD video of a hawk in a tree, on a mountain, in the distance. Will upload to you tube with acceptable Quality "My Standard of Quality" when rendered at 70%. It could be better, but Acceptable is the key here. 66% is Unacceptable for the same video.
60% is good enough for most still Images and lower quality video. Even lower settings work for some things.
I can Guess my way to a high enough render setting every time, that's easy. But for the reasons above and more, It's less than an acceptable trade off. I didn't see any benefit to myself by upgrading to 8.5 anyway.