That's a good question, D. I don't have either one but I debated about getting one a few months ago. I decided against it because:
1. I bought a laptop and can download books, etc. on that.
2. I got a smartphone. If you have an iPhone or a smartphone, you can do pretty much the same thing as on a Nook or Kindle. It's just a little smaller screen.
3. I like my books. I like holding my books, writing and highlighting in my books, looking at my books on the shelves, tables, and floor. If I want to loan out a book (which is very rare since they almost never come back), I can do that. I don't think I would give someone my Nook to borrow.
So, those are my reasons I didn't get one. However, if I had lots of money to spend, I'd have one just for the coolness factor. It's just a matter of personal preference. For me, it would be a waste of money because, even with my laptop and phone, I've only downloaded one book to read...and that was because it was the only way that was available to read the damn thing.
Hope that helps. But...I say, if you want one, get one!!!!!