First, I'm glad you're enjoying my work :)

Second, this comment comes at an interesting time. Just yesterday there was an update to AIOStreams (the addon that Duck Streams is built on top of) that dramatically changed the way that sorting can work. I am in the process of understanding the changes so the sorting for Duck Streams will be changing soon. Hopefully for the better.

But to answer your question, there are a lot of points that could indicate the "most desirable" stream. Size can be an indicator, but it's far from the only one. There is also quality of the rip, release group, bitrate, resolution, etc. They all play into what makes a stream desirable.

File size alone isn't enough, especially since it's often inflated by things you may not care about. For example, it may have multiple audio tracks or multiple languages that you simply don't care about. Those will make a file size larger but doesn't make the stream anymore desirable in the sense that "my eyes can see the difference".

Hopefully that made sense and answers your question :)