I was in a similar boat not even a month ago, shopping for an LR3 or LR4. I'd previously had a 2007 Range Rover Sport so I was familiar with the LR3 era vehicles.
As for reliability, finding a properly maintained vehicle will be your best bet. Things like transmission, differentials, and transfer fluid are often neglected and if not done can end up costing you a lot of money if they fail. Check the passenger side floorboard and headliner for signs of water damage; chasing and fixing water leaks is a massive pain in the ****.
I personally wouldn't even consider a US spec gas powered V6 LR3 due to the lack of power, and I think they're rated for a whopping 1 mpg better than the V8 alternatives.
If you're looking for an LR4, I avoided the '11 and '12 model years because of the timing chain issues; if I had found one with that work done and documented I would buy one, otherwise plan on spending $4500-6500 to get it done before your engine blows up and costs you $10k. I bought a '13 LR4 simply because they had the updated timing components and I preferred the V8 over the '14+ supercharged V6 engines.
The day I bought mine I also bought the following items:
1. GAP IID tool. It will pay for itself within a year if you get any faults or codes that you want to read. Can also program keys if you don't get a 2nd with your vehicle.
2. Differential fluids and transfer case fluids - will change myself because they're not too hard.
3. Transmission fluid and easy-install pan from Atlantic British, will be paying a shop to do this one, it's a PITA even with the easy install pan.
Don't let your worries about unreliability keep you from trying one. I bought my Range Rover with no experience and no planning and it costed me thousands of dollars. Even with all of its faults I still loved it, and I'm glad to be back in a Rover!
. After being familiar with my previous V6 LR3 and no major issues after 280k km, I was comfortable with another one.
