Scott
The rear opening tents are nice, but have a couple of disadvantages...
1. They can only be as wide as your vehicle. The average off road tyoe vehicle is probably about 55" wide, so that means a farily small tent - good for two people, but impossible for a family trip.
2. They can complicate access to the rear of the vehicle.
A side opening tent, allowing occupants to sleep perpendicular to the center line of the vehile, can offer more width = more room for occupants, and can be set up to open to either the Passenger or driver's side.
So the bigger tents are going to be side openers.
M