DM: am I right in saying the new Cayennes have ditched most of the fancy 4x4 tech they used to have?
It used to be the case that RR > Cayenne > RR Sport in terms of offroad performance, but if Porsche decided to ditch the low range gearbox and locking diffs (Like I think they have for the new model?) then the it'll probably be "only" as competent as the RR Sport when the going gets rough.
Not that any of that matters really, its a building site not a rainforest in Brazil
My advice is go for a 6 month old proper Range Rover, all the toys, probably with the TDV8 in it. There are 52 within 100miles of me using Land Rovers AUV search, so your choice is endless.
Still not convinced? Find one used in the spec you like, then check that against the new list price. They've lost 10-20k in a year in some cases

You'd have to be crazy to buy a brand new Sport over a 6 month old Rangie IMO