Man this is a fantastic question, and very well laid out. I am afraid it is a difficult one to answer. YouTube values watch time... so inherently you are going to think that it is the 30 minute video with the 33% AVD that wins out. It gained 10 minutes of watch time on average versus the shorter video's 7 minutes.
What complicates things is that the shorter video is likely showing more end screens and suggested videos. If more viewers are seeing the end screens of the shorter video and then moving on and watching other videos as a result then it is garnering more Studio watch time. This is the time that someone spends watching videos in YouTube as a result of a video and although it is not something that we are shown analytics for it definitely is something that comes into play when YouTube is considering sharing a video out.
So while your 10 minutes of AVD by the longer video is a good number and likely to push that video, you can make a 10 minute video more successful by focusing on keeping your viewers until the end screens and utilizing the view machine (end screen elements, pinned comments, cards and video links in the description).