Casting is cheaper if you aren't buying a bumch of molds to experiment with. With casting you are relegated to the mold's capabilities such as hollow point or not, and sizing the finished slug down in diameter if need be. About the only thing I do with my casting pot anymore is melt spent lead for ingots to stack up.
Swaging is more precise and is about as expensive and time consuming an experiment as you can get. The initial cost is three times as expensive as casting equipment and molds. However, wiith swaging you have a lot of variables that you can play around with like length, weight, hollow point or not, and different base types, and then you can size them down too. So the one die set can do multiple different gun barrel/slug accuracy demand combinations in the same caliber.