I'd take Andre johnson because he is a younger player coming into his own. Horn is older and has put up very goog numbers over the last few years, but he just got a big deal and is getting older.
Also with understand at home distractions this year.. I could see Horn and the Saints as a whole as having a down year.
One more thing.. the saints have a new Offensive coordinator
this year .. so who knows how many touches he will get.