It is probably a matter of taste and what you are going to do with it.
It is probably worth it to note that the Patrol, even with standard suspension (ie no lift whatsoever) is still a very capable off-road vehichle. If you are doing this because you only think you need to, then the best advice is do nothing.
Save the money, and do something that will actually help you.
As for the 4" VS 6": here is a few things to consider:
-A higher lift gives more ground clearance.
-A higher lift "usually" has more travel and will therefore have more tire on the dirt giving better traction. (assuming you didn't just use spacers to lift it.)
-A higher lift kit will have more body roll (especially around corners) and could be a factor if someone in the vehicle is prone to motion sickness
-A higher lift kit causes a higher centre of gravity and "could" cause the vehicle to topple over. (I've never actually seen this happen as is only truly applicable if you really go extreme.)
-A higher lift kit usually sags more when loaded.
-A Patrol (that is already by itself a high vehicle) becomes a lot harder to load and unlaod (especially on the roofrack) with a higher lift kit.
Thre are probably a few other things that I can't think off-hand that compares the two, but there is just one more cosmetic thing. If you lift your suspension, put in bigger tires, because it looks just sad to have a huge vehicle seperated between body and tiny wheels far below.
Other things you might want to consider when lifting your vehicle:
Loading conditions - if you plan to regularly overload your vehichlee, then make sure you put heavy duty suspension in the back. However if you don;t plan to regularly overload it, DO NOT put heavy duty suspension in as it will make the ride hard and uncomfortable. You can alternatively just support the suspension with air which you can adjust for each loading condition. This however reduces the travel a bit.
OME (and other suppliers) often have a coil that is tapered at the top. This makes the ride nice and soft for tar roads when not heavily loaded, but still offers a durable and long traveling suspension when under heavy stress.
DO NOT LET LA SPORT in Pretoria install the lift kit. I had to take mine back a few times before it was finally right.
Lifting the vehicle by too much could interfere with the steering. (quite few people have complained about having more wobble at 100 kph after their lift.)
Make sure your steering is straightened again after the lift.
Anyone else has something to add that I might have missed? Peter?
May the road be long.. and dirty.