1. Winter tires
are unsafe in the summer, as soon as the outside temperature goes above 15 *C, braking and handling abilities already drop compared to summer tires, not to speak about the excessive tire wear when temperatures rise.
2. the 20'' Sport Technos with Michelin Diamaris don't really have an advantage, oh well, they look nice and handling might be improved slightly. But you get a stiffer ride (even with air suspension, especially if you locked it to the sport setting) and the tires
and rims are much more likely to be damaged even in less rough terrain (if you still want to go a little bit off-road). For street use only, I'd say go for them (I got them too for my Cayenne Turbo) but if you're doing a little off-roading from time to time or if comfort is the main priority to you, you might want to reconsider.
A little comment regarding 22'' wheels: absolutely
not recommended. Besides the fact that 22'' rims are usually (depending on the manufacturer) really heavy and the mounted tires usually aren't always to Porsche safety specs (speed and especially load index!), the damage of a 22'' can happen very often, even when driving on the street only. I've been shocked by the distance from the pavement to the rim when I looked at one of those 22'' rims. You just have to drive through a tiny pothole and you already damage your rim and maybe even the tire. Absolutely not recommended!
Not talking about the fact that Porsche
will very likely void the air suspension warranty for 22'' equipped Cayenne (I bet the dealer who sold you this stuff didn't tell ya...
).