First I have to say I am an advocate for all four matched tires, it avoids all this. Having said that when I put the snows or summers on I put the better tires up front (maybe .5 mil better tread). While it is true that with a better griping tire up front you are more likely to over-steer that is just one component of driving. Straight out braking you will stop faster with better tires up front becasue most of the stopping force is on the front tires not the rears and avoiding a collision by rapid braking is the most common practice to avoid accidents in the first place. Also being front wheel drive, having better tires up front gets you moving and more importantly not getting stuck in the first place.
Again I don't run mis-matched tires and don't recommend it. I rotate to often, 5k miles and look at the tires when I do, but these are things to consider as well.