I made that choice some weeks ago. First I got an e-reader, though none with e-ink. I aimed at reading pdf manuals. It was a very disappointing experience. I sent it back.
I then got a galaxy Note 10.1. Super choice. Reading pdf's of any formatting is no problem, the display resolution is fully sufficient, the documents at any zoom level are crystal clear and sharp, you do not note single pixels if you do not really examine the display closely - I have read for up to one hour without any problem to my eyes. Plus the thing can do so much more than just an e-reader. Also, you escape the Amazon-chain-ganging, if I may call it so.
I do a lot of surfing with it now, too, it is more comfortable than sitting at my desktop for that. I also use it for Chess, Abalone, and the like. I also used the options of having electronic maps with me on bike tours already.
Yesterday it also saved me. My PC did not boot due to - as I later found out - dust or a broken USB wire causing the USB system shortcutting. I would not have found out that information so qickly if I would not have had a second backup internet access.
I think e-readers sooner or later will disappear from the market again. Even their handling is not as comfortable as that of a tablet. Same for resizing pdf formats.
Tablet over e-reader any time!
Books I prefer as printed editions, however. Neither tablet nor e-reader compares to fast turning pages in a hardcopy book when searching or wanting to compare different passages. Plus the fact that you do never own electronic books you have payed money for. You cannot give them away, and Amazon can delete them all by pushing a button. And they have demonstrated to do that if you travel for example to another continent, there want to use your Kindle to buy in the local Amazon store - and the fineprint then has told you that that not only is not allowed, but that it makes your e-library and rights void and deletes your account. Nice, eh?
E-books only when they are free. When they cost money, it is stupid to buy them.
Display qualities in sun light vary with devices. In direct sunlight, almost all LCD screen must surrender. However, the Note 10.1'S screen is said to be one of the best regarding reading possibility in bright conditions, it cna easily be chnaged. Battery life in normal room conditions is around 11-12 hours. However, Li-batteries are better not emptied, but you should recharge them if possible even at 90% capacity again, and bring them down to below 20% just every 6-8 weeks or so to reset the battery capacity sensor. Not dechragiung Lithium batteries too much if you can avoid it helps to increase their lifespan.
The Kindle has an advantage on battery, of course. Running several days or weeks without charging, depending on your reading habits.
P.'S. I know there are tablets with higher resolution than the Galaxy Note 10.1. However: does one really need that if you already do not note single pixels on the Note? The retina sucks much more power, the battery thus does not hold as long. And you need more of the CPU's power to run the display. The Note 10.1 also has 2 GB RAM - twice as much as most if not all tablets there are currently. I run X-plane and quite some complex stuff on it! It also offers multitasking and split screen action in two simultaneous windows, and it has an integrated, pressure sensitive pen: the brush in your painting app spreads the more the harder you press they key. If you consider the Kindle Fire, go all the way, its better results in the end: skip the Fire and go for the Galaxy. I love mine for sure.