My view on the subject is that the good tires go - on all four wheels period!
Regardless of the drivetrain, putting worn or simply old tyres on one axle will reduce it's grip levels more substantially than any other variant (worn dampers, wheel alignment, balance, etc...) and make it more prone of sliding. Even a difference of one year of age, regardless of milleage or tread wear, can have an effect!
It's important to mention that worn tyres will not alter the car's natural handling characteristics: All modern cars are adjusted for an inherent understeer (when driven "on the throttle") and if the rear tyres are very worn or aged, the car will not naturally lean to oversteer but, once the required measures are taken (sudden closure of throttle, sudden braking or sudden throttle in a RWD) the oversteer would build up faster and be much stronger than it would be with proper tires.
Having the good tyres on the rear isn't much better either, due to an increased understeer (which could also turn into oversteer very suddenly) but also and mainly -
Dramatically increased stopping distances. Another problem with having the good tyres on the front or rear, is that the ability to perform regular tyre rotation cycles is effectivelly eliminated, along with it's various advantages.
As I understand it, the latest advice is to avoid rotating tyres. Tyres "bed-in" to their placement on the car.
Tyres don't 'bed' into a specific place on the car, but rather to a certain direction of rotation (assuming they already have enough miles on them prior to the first rotation). To solve this, one should remove the tyres from the rims, which is a good oppurtunity to have them inspected all around, and than have them fitted on the opposite rim, e.g. front-left tyre to rear-right rim. This way, not only is the direction of rotation maintained, but the tyre gets rotated over the rim, so that the worn outer shoulder is now inserted towards the inside.
The only excpetion is with assymetic tyres, which are rotated simply by moving the front pair to the rear, again while keeping them in the same direction of rotation by rotating them on the rims.
Returning to the original subject, if the differences between the tyres are significant enough to lead one to wonder as to where to put the good pair - than all four tires need to be replaced! Differences of under eighteen months or 9,300 miles are not considered substantial.