Performance should not be much different if we compare changing tabs with RadMaps inside or changing the kind of the Map's provider runtime. However, I think the bigger question is usability - what will clients expect in such application. For example clients may need to pan and zoom in the Bing RadMap , then go to the OpenStreetMap and then return to the BingMap and they may want to have the previous pan and zoom settings preserved. With TabControl / PaneGroup this is simple - just set IsContentPreserved = True.
With "changing-providers-runtime" approach this would requirement much more code.
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