What are the minimal screen parameters for tablet bought for reading papers Kind of related to my last question: Is typical ebook reader with pdf support enough to read scientific papers (but I guess that this is distict enough). 

What are minimal sreeen parameters for tablet so I can read papers with ease:


is 7'' screen size enough, or do I need 10''? I figured out that 5'' is not enough (to much scrolling). 
Is getting additional 3'' (from 7'' to 10'') worth about 70% price increase? 
is iPad's retina display (2048 x 1536) really usefull or I can stick to cheaper tablets?
The screen size really depends on how much scrolling/zooming you want to do...I would suggest trying both the 7" and 10" out in person.

As for the retina display, text is going to be much sharper. Again, I would check this out in person.