Many reviews I've read failed to mention the differences between the 12.9" and 9.7" split view mode. For those still trying to decide between the 2, I recommend reading the MacStories 12.9 review which I think helped a lot in my decision to go with the 12.9". The difference is more than just a bigger screen for many apps when used in split view.
This is the biggest (only?) reason I want the 12.9".... Having a full side PDF and a full-size page of notes is just awesome. But alas... trading is hard where I am, and I don't really have the means to own both