I prefer the buttons for turning pages, but I'd want to keep the touch screen for selecting books, moving between screens, changing fonts, etc.
I did have a good chuckle at myself when I realized that part of the reason I like buttons for page turns was that the longer time elapses between eye exams/new glasses, the further away I hold the reader as I read. Turning the pages with the buttons, using the same hand holding the reader, is just easier when you're extending your arm a good distance from your body.
When my eyeglasses and their prescription are brand new, I hold the reader closer, and I find I alternate between using the buttons to turn pages and swiping.
I do also agree with the fingerprint/smears thing. I certainly don't have to clean my ereader screens as often as I do my phone, but I definitely have to periodically.