There's really not a one-size-fits-all solution for everyone. The options you listed seem to be larger devices with pen support, so is that what you're in the market for? I ask because the best pure ebook reader device is not necessarily the best device for PDF reading/annotation. Bigger screens are better for those--you really need at least a 10-inch screen if you want to comfortably read or edit PDFs. As close to a standard 8.5x11" piece of paper as you can get, ideally, because the majority of PDFs that you would be annotating will likely be physical paper scans.
But if all you're reading are ebooks in formats that support text reflow (EPUB,MOBI,etc.), you can get away with the normal 6" readers, with the advantage that they're smaller and more portable, and cause less fatigue to hold in your hands for extended periods.
Of the smaller e-readers, I personally favor the Kobo. The Clara HD had slightly better specs than the equivalent Kindle Paperwhite when it came out, in addition to better supporting the things I care about (like STANDARD ebook formats, Pocket integration, and Overdrive integration). So that was the right decision for me. But for my family, I've just recommended they get the Kindle Paperwhite, because most of them don't care about trying to pull their books out of the Amazon ecosystem.