One set of potential use cases of mine would be very similar to yours (plus I'd love to be able to use such a device in teaching, ideally with miracast, but that seems currently unsupported by onyx, see my thread on the issue).
I don't have a large ereader yet, but I'm pretty much set on the Note if the price drops a bit and/or they include sd-card + hdmi.
In terms of size, I'm quite happily using my 8 inch Venue 8 Pro for reading academic pdfs (but then I don't annotate that much and have relatively good eyes). On my 10 inch tablet, there's plenty of space, so for me personally 13 inch would be overkill and I'd much prefer the reduced weight of the Note. But of course that's a matter of personal preference and there definitely seem to be people who find using the 13 inch device much more comfortable.
If you have a chance to try a 10 inch tablet around somewhere, I'd suggest you have a look at some pdfs on that to decide if you're fine with the size.
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