The problem with the kindle is you have to buy from Amazon. For that reason I went with a Sony reader and I
it because I can buy my books from Sony's store or Kobo (which tends to have the best pricing). This gave me access to the best selection of books and the best pricing.
The Kobo reader's also pretty damned affordable. I opted for the Sony instead because it's got a metal frame and is more sturdy and the thing is in my purse or in a bag often and I wanted something I wasn't worried about getting broken if it got knocked around. Also the Sony allows me to load PDFs and other work related documents on it, not that I use it that way often but it has come in handy before for short meetings.
If you're mostly going to use it at home, any of the big three would work well for you I'm sure. But price match a bit between Amazon and Kobo on the kinds of books you like to read and their selection.