Going back to ... Back
When I first got my RTT, I mounted it opening sideways. Then I quickly turned it to open over the rear. after a couple of years, I decided to turn it sideways again and now I'm regretting it. I will be turning it to the rear soon I think.
Rear Pros:
some more shelter than the tail glass provides
Easier to access the side window tension rod holes (this is the biggest pro), allowing much safer and faster setup
Can go out the front door onto the roof rack. Kids love this. also nice for shoe and duffel placement
sometimes it is easier to camp in tight spots, against trees, or parked with multiple vehicles in a tight spot
Easier to determine if vehicle is level front to rear... Subjective, but it seems easier for me to park tail down slightly and still sleep well.
easier to open and to reach across the top of tent with it closed
You are never on the wrong side of the vehicle.
Rear Cons:
Door opens within 1-2" of ladder (Tepui Ayer and Jeep JKU)
On my tent the travel cover has to open back or forward, hanging over your work area or flopping onto your rooftop gear. I will probably fix this with some custom sewing next time I rotate it.
must remove CB antenna to close tailgate with tent open. I have a quick release, but still forget (or the kid does), and have come close to breaking my antenna several times.
Side Pros:
Travel cover hangs under ladder in "dead space"
No antenna concerns
Side Cons:
Travel Cover covers back door of Jeep, inevitably kid decides this is the ONLY door that can be used for whatever she needs.
Reaching the front tension rod that is over the center of the Jeep Roof is a really sketchy activity, especially in rain, snow, ice.
Tucking material across the center of jeep roof after folding is also a difficult reach.
All in all, this is a "to each his own situation", but it is also the Internet, so everyone else is automatically wrong! Except for those that agree with me... they are simply not wrong until I change my opinion!