D4's are very good. Although I personally prefer the D3 styling wise. The lights on the D4 are a bit chavy and chintzy in their blingness.
But overall there is very little on the market that can do what the D4 can. For me the biggest issue is the engine. While there are plenty that have been fine and have covered huge mileages. There does seem to be an ever increasing count of snapped crankshafts.... As long as you go in eyes open on this point, I don't think you should be disappointed.
Trim wise. The higher the spec the better is normally true for most cars, the D4 included. Worth reading up on the differing trim specs.
If you don't need the 7 seat capability or boxy interior shape, obvious alternatives would be the Range Rover Sport L320, as they are built on the same platform and technology. But can be had with the far superior 3.6 TDV8 or a petrol V8. Or the L322 Range Rover which include those engines and the brilliant 4.4 TDV8.
Don't get me wrong, the TDV6 is actually a very good engine in all other respects. But you just can't tell if one will snap its crank or not in advance. And if it does, it is new engine time. Which won't be the cheapest of things to do.