There is a lot to like about MarginNote, but I am currently using Liquid Paper because of one thing that MarginNote lacks – it does not sync the reading position of the document. That is, if I close the document on page 42, I want it to open to page 42, even on another device. I hope this is on your roadmap for implementation.
İ sometimes use liqudtext too. But it d not be fair judgement if i dont use MN for just this reason.
You can easily arrange last used screen random capture to mind map and keep working with one click on another device if sycn working well.