For mileage - higher pressure
For tire wear - Take a pain pen and draw a line across the tread on a front and rear tire.
Drive straight for about a block.
Take a look at the line.
If the line is gone in the middle and not the sides, too much air. If gone on the sides and not the middle, too little air. All gone just perfect. Rear will be a lot less than the front.
When I do this it is usually at cold tire pressure. So I make sure that I am wearing on the outside just a little bit.