I have both a Nook Color and an iPad which allows me to read both Nook and Kindle editions. If one finds a book in both formats, is there an advantage to buying one over the other? I almost exclusively use my iPad which has both apps installed. Just wondering if one format gives a little extra over the other. I notice that this particular ebook is twice the price in the Nook format. Is that due to that format having some quality or feature advantages? Thanx!