[Salgueiros]

I use Kindle DX to read research papers like the ones you have shown and it works perfectly. Text is easy to read and the equations and graphs are displayed very nicely in it. The resolution is enough to display fine lines and small characters (like the greek letters in equations with remarkable detail). Some PDF's offer the option to remove the margins but even when you do not remove them, it is perfectly legible.
The only thing that is missing is the highlight function and notes, but I use Mendeley for that.

I would not recommend anything with a screen size smaller than 9' to read non reflowable A4 PDF's which is the case of journal papers. If you can't afford a Kindle DX or similar, i would stick with paper for now. But if you can, go for it. It is amazing to carry almost all your journal paper under your arm or in your case ready to be read and organized in folders. My desk was never the same after i got the DX...