I know this topic is quite common, I just wanted your thoughts, whether staggered wheels (same diameter, different width) are recommended for an AWD car like X5?

I am currently looking to buy new set of wheels and all the retailers whom I have spoken to, unanimously advise me not to buy staggered wheels for my X5. They say that staggered wheels ruin the transmission and the drive train. But this is contradictory to the stock 21" wheels that BMW provides, since they themselves are staggered.

Does BMW programs a staggered stock wheels equipped car in such a way that the car 'knows' it is running on staggered wheels and thus the transmission handles the drive/shifts accordingly?

Anyone using staggered wheels on their X5? What do you think it improves and degrades in terms of performance/durability/handling/cornering/etc? Any insights as to why or why not staggered wheels should be installed in an AWD car?