Go for the Wagon. I did. The added utility of the back end is real and useful. And, the Wagon does not give up much to the sedan. It is a few hundred pounds heavier and the sway bars are a little softer (probably my first mod will be heavier rear sway bar). And, if you want to mod it, it will take 90 % of the mods the sedan will. There are some differences in what you can do to the suspension/wheels since the Wagon fenders are a tighter fit than the sedans..... but, from what I've seen it is apparently possible to swap the front fenders for sedan fenders...... but I digress.
Go for the Wagon.