*IF* battery or glare or whatever it is that concerns people about LCD screens doesn't bother you then go for the 7 inch Fire tablet. You can use the Kindle app from there, or for even more elite status use the Calibre Companion app. It is a more functional device whereas the ereader is only an ereader. It also has more storage which I understand is an issue with comics. Any Kindle besides the KO2 is 4 gb
But go try one out somewhere because the ereader likely has a 300 ppi screen which is better than the Fire. Has better battery life, and if you buy all your comics from Amazon and regularly remove your unread stuff then then it sounds like you can safely rely on the cloud and the aforementioned is a nonissue.
Good luck,