IMO, you won't get the level of post-sale support that you would on the other two devices.
Between the Moto X & Droid Maxx though, the Moto X lacks the amount built in memory of your current phone, so that probably could be a non-starter. OTOH, one drawback of the Droid Maxx is that it doesn't have the best resolution for a phone with its screen size. Also, the larger size may make it slightly harder to hold than either the Moto X (or your current iPhone 4, for that matter).
It's all about tradeoffs. If you were w/ ATT, they offer a carrier exclusive 32GB version of the Moto X, which seems like a slightly better fit perhaps.
Hope that helps.