Crowdsourced Shopping

Captain Vorpatril's Alliance is available in electronic format, and I want something to read on the train, so I'm looking at ereaders. Are there overwhelming reasons to go with a Kindle Touch over a Nook Simple Touch? Available free / cheap books, breadth / depth of compatible file formats, convenience of downloading internet content, marginal non-reading bonus features? I'm leaning toward the Nook. I'm also eying the Sony ereader in reflexive anti-crowd attitude, but I'm not buying without trying.