It would depend on the spices that you use.
For fresh spices - whole pieces of cardamon/ cloves/ cinnamon etc., I would add these spices at the beginning with hot oil, so the aroma of these spices would release to the oil. Stewing it slowly would also make the flavor slowly develops.
For adding at the end, maybe you mean adding the garam masala powder. This powder could add back some "kicks" or highlight as some of the "volatile" aromas are lost after cooking.
However, there is not a clear cut between methods 1 and 2, instead, you can add fresh spices at the begining and garam masala powder at the end. Just to make sure that the flavor is kept balanced when you use both methods.