I wish there was a third option for how much time you use paper books also.
Unfortunately, ebooks don't seem to really support equations yet, so for books, I still resort to paper books (or google books on my computer). For reading papers, I mostly use my ereader- but since they are pdf's I'd definitely recommend a larger screen device. For research, where I'm flipping back and forth between 4 papers and such, I end up using my computer because it's easier to have them all open, and scrolling through the pages are faster. (And, of course, I often need my computer anyway to run mathematica.)
As for particulars, I'm a Ph.D. student in theoretical particle physics. I have a Kindle DX. I certainly wouldn't get anything with a smaller screen, but pdf support is pretty bad. On the other hand, I haven't really found anything with much better pdf support. The big thing that the kindle line does is automatically crop each page; as far as I know, no other device does that yet. However, it doesn't support hyperlinks which drives me crazy.
Hope that helps!
|