I spent 6 months in a RTT. I would not advise ever spending the top whack rices for them as you've righly said it's JUST a tent on the roof. for 2k you could buy an amazing ground tent set up!! That being said there are obviously benefits and I'm sure you know what they are.
I got my tent with the car when I bought it. The tent has no labels so I'm sure it was from one of the companies you can see on Alibaba or similar Chinese eBay type sites. Here's the things to look for, and I mean look for, GO AND SEE IT! If you can't make sure you can send it back. I believe most of the cheaper options come in bits and you have to put them together which could include drilling holes and sticking patches.
1) FITTING. If there is a poor fit around a corner or fold you will be left desperately trying to close a persistent gap. Not a huge problem here, but I spent many night stuffing clothes to plug up sizeable holes where the material didn't quite close around a hing or something to try and keep the mosquitoes out.
2) FLAPPING. My tent has surprised me with it's strength as I've had it up in some incredible winds, but the damn thing can flap about and when you're inside and a heavy cloth tent is flapping right next to your head you will not get any sleep. Is the material tight? Does the poles stretch out the fabric when it's put up?
3) AIR. It will get damp under the mattress. In colder months more so. being able to air the whole thing is a must. Under the foam matress is where the water collects and big side panels that open up to let the air in are very very useful.
4) STRAPS: The bag that goes over the whole thing when it's folded away will take a bashing, not least when you're driving along at the 120 MPH that we all know defenders do. There are straps that fold over and hold the bag down to stop it flapping it's self to death, my have all broken. I have purchessed thicker webbing and metal buckles and so far so much the better.
I think thats about it. I have water proofed the material and that mad a great difference. I'm buying some under mattress air channeling material to help with condensation, and I have a way of setting it up / parking the car / trying everything down so that the flapping is reduced. I love my set up. I can defenetly see what you may get when you spend the big bucks, but I was happy with a bottom end of the market tent. In the end. Camping in the UK is always going to be wet, windy and cold.
