Mostly the sedan & the wagon are identical, mostly. The main difference is that the sedan has a wider stance than the wagon. This makes some suspension upgrades a little tricky, but from what I've seen the wagon folk are very crafty and can make most things fit one way or another, even if it's not a wagon-specific part.
I ended up with a wagon after starting to look for a sedan. Bear in mind that the ladies love the fold down seats; the sedan guys will never be able to top that .