Using an electronic device for reading, advice please.

Because of my eyes I find it easiest to read on a screen. Typically I read PDFs/ebooks/etc and quite often I annotate PDFs (ie comment on student reports). I’ve been using my 11” iPad for this and the screen is nice, software alternatives are OK, etc … but it’s a bit heavy. A couple of years ago I tried a Kindle (I’ve forgotten which model) but I disliked the screen (greenish, low resolution, etc), the slow software, etc, but the weight was really nice.

Anyway, I’m considering getting some dedicated reading device but I don’t really know what alternatives I have. The obvious to me is the iPad mini but are there other devices I should look at? Note that the ability to annotate a PDF and being able to send the PDF back to the student is a really important feature.