Major difference factor for me is the size: I had a 10" iPad, then a Nexus 7, which was great. Fit in any pocket. Then I had an iPad Mini, which was a gift from my Mother, but I didn't like the size. She repossessed it, and I tried the Asus 8" - I think I got a bad one. Now I have the Tab S 8.4. Fits many, many pockets, and is light enough to hold in one hand while reading. So...
Size is the issue. Dimensions and weight should be considered. Anything too heavy is very hard to hold in one hand for any period of time. If you do read on your tablet, and you can't always guarantee a table to put it on, think hard about the weight.