I have the Nook touch & the Kindle Touch. You do get used to the Nook size. I'm not fond of the page turn buttons though. I find them a little stiff, but I'm sure if I used them enough, I would get used to them.
Get a Nook from Best Buy & try it for a week or so. You can return it if you don't like it.
I have 3 e-readers (Nook, Kindle & Sony). I like each for a reason & then there are some reasons I don't like them. But I found I can get used to just about any reader. Many amazon books I find I can buy at smashwords...Not all but a lot of them. Depends what kind of books you are looking for.