The privately imported BMW prices are for sure cheaper than the swiss dealers based cars. Because you will not get 10 years/100.000km free of service (laborship). I would not bring the car to a BMW official delaer for a service, they would charge as high as possible.
If you are thinking of re-selling the car, it is smt not favorable in CH.
At the end, it is the same car, and less money invested.
So totally your decision!