I stayed in all of them a couple of times.
I really like the Miss Clara by Nobis because I find historic hotels / hotels in historic buildings interesting even though the rooms are small. The Nobis is nice as well. The Sheraton is just huge and nothing special. The Stallmastaregarden Hotel (what a name...) is nice as well, but the location is not ideal for city trip. But if you want an excellent restaurant and a clam and cozy hotel the Stallmastaregarden is a good option.