Consensus from the 2018 iPad Pro reviews seems to be that the hardware is amazing, but that iOS continues to be too limited. That seems fair, and I expect iOS 13 to be the release where that changes. The gap is smaller than you think.
@kaa tried them yesterday. The screen on the 12.9 is stunning. Being able to use two apps side by side without being scaled to compact size class is great. But, yeah, it’s still huge compared to the 11. Still not final, but I’m currently thinking the smaller one is right for me.