No low cost interest on the 2 year old X5 but you might be able to drive a hard deal on it and also because its lost a fortune in years 1 and 2 you are at a sweet point of depreciation. You may find a PCP not too bad but on other hand it could be a similar figure to leasing a new car.
This is a debate I've had in my head many times and sometimes leasing seems th only way, other times buy a 2 year old car and put down a hefty deposit if available sounds wise.
The example above about the Civic isn't really apples for apples. Yes it will cost a lot more to PCP and get a new car every 3 years but thats the point, you drive a max 3 year old car and get a brand spanker every time. That to most peoples minds can't be considered the same as keeping one car for 9 or 10 years and then changing which will always be a cheaper option unless repairs kick in but you are always driving an older car, to some that doesn't matter but to others it would.