I haven't used the Kindle Fire but on the Galaxy 2, you can change the font size, you can change the backlight level, you can also change it to black background/ white font or sepia. Very easy to read. What I like about it that's better than the Kindle Touch is that you can turn the tablet horizontal and read. I then hold it with both hands like you might a book. I imagine that its the same quality as the Kindle Fire with the same options. Its just that for $50 more you get a camera and the ability to add memory.
The only thing I don't like about my Samsung Galaxy Tab 2 7.0 tablet (and it's a minor issue) is the screen glare--and that will be true on the Kindle Fire too. Your best bet is to look at the tablets and Kindles in a store if you can and see how much this will bug you. For me, it is a minor issue, so I went with a tablet that I can use for all kinds of content.
When buying for a friend, I went for the non-tablet style Kindle because I thought she'd like the the paper-like look better and will be more comfortable buying all of her books from Amazon. She's technologically challenged, so simplicity of buying and loading books also drove my decision.
It depends on what u prefer. Many prefer Kindle readers over a tablet ,although I like the kindle app on Samsung galaxy tab2 brightness is adjustable and I use the tab for all my books Kindle really gets particular with there readers and it's good to have a choice.
It may not be as good as an older Kindle with reflective screen, but it is as good as a Kindle Fire with the LCD screen. Actually, to me, it's better, because I use other ebook readers (mostly Moon+ reader), which has a lot more features than the Kindle reader. Also, it can read a lot more formats although using Calibre on my main computer, that doesn't matter very much as it can convert just about any format, and send it to the device.
All the adjustments are controlled by the reader software (Kindle app, Nook app, etc.) not the Galaxy, and yest, the apps contain those setting changes. The downside is the glare off the Galaxy screen may make it difficult to read under certain conditions. I bought a matte glare screen for mine and it reads much better.