I used to always put the news on the front as you assume they do most of the work, keep in
mind though that if you loose the back end the car will spin around.
Just now I have gone through the exercise of rotating the wheels the wheels on my prado, tyres
fitted where Coopers St Max, they have done around 30000Kms and half of this was on goat tracks,
gravel and sand.
On inspecting the tires, van (Vista XL) little damage tread probably down about 1/4, car fronts, little
damage again tread down about 1/4. Car rears, some chipping more wear and tear to tread blocks
tread depth down about a 1/4.
So in my particular case the rears are doing more work so I be more inclined to put the new on the rear and
the rears to the front to extend their life.