For the PDFs I use, reflow is totally useless. And there's no landscape viewing on Nook. Nook also does not support PDF bookmarks or links. No annotation.
So Touch and now Paperwhite are much better for my usage. The higher resolution of Paperwhite helps a little also. Most of the time what works best is to put it in landscape, which crops whitespace margins automatically and things are easier to read. But you can also double tap to put it into 'column nav' mode so it zooms and auto-crops in portrait. If you have any tables though, it gets a bit strange.
Sony PRS-Tx is a little better than Kindle since it allows on-device cropping (auto or manual) that sticks between reading sessions.