Currently using the Voyager, although I've used the Paperwhite and various older models. I love the Voyager, but honestly the Paperwhite model is 95% as good. The text on both are a bit crisper then on the $80 model, but it's not like the cheap model is crap by any means.
IMHO the Paperwhite is the price/performance winner by a large margin. Don't forget Amazon has a good return program and there are a bunch of free books available so it's easy to try it out with little to no risk.
I've never wished for a larger screen (the 6" is just fine) and you can change the font size to match your vision- you can go really big actually. The OMOTON case for the Kindle are inexpensive and work great.
The trick to get lots of free book credits (also good on video games and movies) is:
1) Buy a bunch of crap on Amazon. I almost never walk into a store so that's easy for me.
2) Check out one item at a time. Most, not all orders are good for the bonus credit.
3) If you're buying multiple of the same thing and actually want it 2-day, order all but one via the slow-credit method and the last one via 2-day Prime. About 80% of the time all of the things end up shipping together so I get both the $1 credits and free two day shipping.
4) Sadly, you don't always get the $1 credit. Sometimes it's a credit for something else ($5 on Amazon Now for example). Usually it will go back to the ebook credits if I a) buy something using the slow ship option AND b) wait a few hours.
Anyways, I just spent a week relaxing in Mexico and between diving, hiking and drinking I finished:
The Terror - Dan Simmons
Way Station - Clifford Simak
The Gunslinger (The Dark Tower Book 1) - Steven King
And half way through Book 2 of The Dark Tower series. All on the Kindle. Would of been a real PITA if I had to drag all those books on the plane.
Quick reviews:
The Terror was awesome- as I've come to expect from Simmons. Great mix of historical fiction and horror. Haven't started watching the mini-series yet, but it's also supposed to be good.
Way Station was the second book by Simak I've read (the other was City) and I guess after City I have to say I was a bit disappointed. City really set a high bar and this just couldn't compete.
This was actually the second time I read The Gunslinger. Wanted to re-read it before diving into The Drawing of Three/Book 2. Amazingly, these are the first two books I've read by King and so far I've been really enjoying his prose and the story. Definitely a bit more fantasy then I'm used to reading, but I love a good spaghetti western and so far it's really kept me guessing.