You see it mostly on performance cars. I've seen that staggered setups can help you achieve better grip in the back, due to the wider tires, but keep handling and cornering ability decent as well.
But most of us don't or rarely track our cars so it's basically just for looks. I personally run it myself and love how the tires and wheels look.
10 or 11 will be equally flush in the back, all the extra width is on the inside.
10” will probably be better balanced at the limit with less understeer, if you drive at 9 or 10 / 10ths of your car’s cornering abilities and like to autox or track the car.
If you don’t drive quite that hard and just want more grip for straight line launches then 11”.
What it really comes down to is tire wear vs launches. Since you daily I suggest going square so you can rotate your tires and get more life out of them.