Originally Posted by S-Dot
Many models come with all-season tires, so you're kind of stuck right out of the gate. Keeping them on provides a compromise to performance for three of the four seasons. I'd rather take strides to maximize my enjoyment during those nine months. I notice the difference between performance summer tires and all-seasons, particularly in moving to a wider set that will provide better grip for braking and cornering.
In the winter, all-seasons provide less grip than winters, but are still more than manageable until they wear out, and then I'll replace them with winter tires on a square 225 setup.
If you really care that much about performance and like to push your BMW to the tire's limits, then you should probably get a RWD BMW that comes with summer tires.