Q: . . . and why?
A: in springtime i would recommend to go to Lugano/Locarno (southern part of Switzerland with already nice and warm weather). on the other hand you could also visit the Lake Geneva region, Geneva, Lausanne, Vevey, Montreux. http://www.myswitzerland.com/en/offer.cfm?category=Destinations_Resorts&subcat=Short%20City%20Breaks&id=111588