Why would you need a trailer if you had the Jeep?
Not sure if you have seen a XV-JP in person, but they are great for a short trip with two people. I would imagine on a longer trip (measured in weeks or months rather than days), you would be looking for extra storage fast. And if it is the kind of trip that requires bringing toys (read: anything too big to fit on the shelf bins like skis, bikes, kayaks) you will need somewhere to keep them/transport them.
It is amazing how much EarthRoamer packed into the Jeep, but the reality is that it is still a Jeep.
I think my dream expedition rig is a Sportsmobile built by EarthRoamer (ER quality is amazing), second probably would be the XV-JP and a trailer for longer outings. IMO no EarthRoamer that I have seen is particularly suitable for a traveling couple or family that wants to bring toys along.