I don't agree that a pickup is better than an SUV for towing if you stay comfortably under max towing capacity and don't need the extra cargo capacity of a truck. I suggest you look at the Grand Cherokee 3.0 diesel if you go with a Grand Cherokee though.
As far as your TT choice, if this is your first towable RV you might want to stay on the shorter/smaller side. Try to rent something before you buy, which will give you a good feel for the experience. We are going on our 3rd RV and they continually get smaller each time we change because driving a large RV around can be a real pain.
If you are used to tents you will probably be outside most of the time anyway, so converting a dinette for sleeping shouldn't be a huge issue.