If you are looking at 2010s, the Range Rover and Range Rover Sport's interiors are no longer on different planets as they were up to MY09 (the Range Rover used to be far more luxurious in just about every way inside the cabin), but other than that, engines and some technology sharing, the two cars are completely separate platforms with totally different characters and a distinctive "feeling" behind the wheel, besides the obvious interior and exterior appearances and dimensions. You may love the fact the RRS fits you like a glove and cocoons you, of find it claustrophobic and uncomfortable. You may prefer the serene and plush, more truck-like ride of the full size, or rather be in something that feels and responds more like a sports car, like the RRS. As money is no object, take as many test drives as you can. The differences between the two models start becoming apparent from the moment you sit behind the wheel.
Reliability is what it is, despite big improvements during the Ford ownership it's not a big secret that Land Rover is still no Lexus (but the cars aren't Lexus cookie-cutter boring, either...) I, for one, have 130K+ miles on my 2006 and could not be happier with my Sport, despite a few minor issues which should be normal on a high-mileage car as capable and high-tech as the RRS. And I dare you to find any car enthusiast forum, regardless of manufacturer, where owners don't eventually stop by to complain about something, we are no different here on rr.net... So, I wouldn't use these forums to accurately gage predicted reliability if you are considering a Range Rover, although you can get a pretty good idea of the most common type of problems you may encounter down the road. If your top priority is trouble-free ownership, you may be better off looking elsewhere. Land Rovers aren't for everyone, and a lot of the technology and cutting edge capabilities of the vehicles - which also make them potentially less reliable than the average as daily drivers - are often overlooked by owners who only buy them for their looks and "cachet", and could care less about taking them off the beaten path (I was one of those owners, until I took an off-road course locally and discovered a whole new car I didn't know I had...) When I was looking to add a dependable SUV for my wife and kids, I thought about Land Rover's trick air suspensions, HDC, Terrain Response, access height, fun-to-drive factor, amazing capabilities both off and on-road, approach and departure angle, and went straight to Acura. :lol:
Finally, your local dealership often makes all the difference in how happy you will be as an owner. Although there are exceptions, in general it would seem many Land Rover dealers still have a lot to learn about courteous customer relationship and service expertise, at least compared to their direct competition in the luxury SUV market, and unfortunately a great salesperson usually gives you zero indications about the efficiency of their service department after you buy. For that type of feedback, a forum like this one can be very helpful.