Rear tire wear is much better than tire wear, for the most part you can still control the car if the rear tires are bad, but you can't steer if the front tires are gone, so it really doesn't matter how much traction you can get with the rears, if you cant steer the car.
It all depends on which drive type the car is obviously ...
I was driving my Skyline R34 in the Polophony Cup ... and the last few laps of 17-20 I had red tyres on the back ... but due to 4WD I could still finish the race with my fronts still being green.
But on FF it near impossible to do ANYTHING once those fronts are red ...
The trick is to setup the car so that all wear even ...