Typically you are better off adding the smoke first and then finishing in the oven. When the water activity of the meat being smoked is higher it allows the smoke constituents to be more readily absorbed into the meat vs. when the meat is dryer and you basically get a surface application of smoke. Try it both ways and you will see the difference. It is not as readily apparent on say a large roast or cut of meat, but if you are doing jerky, smoked salmon, or have already created a good "skin" on your product the smoke does not penetrate and just lays a coat on the surface, if you try to smoke it too much like that it will actually tar the surface. That is why it is better to lay down the level of smoke you want and then finish to proper temp. In certain circumstances it can also create unsafe food products by holding them at unsafe temps for extended periods of time.