The answer to the question, “Which manufacturing method is best for my part?” is, “It depends.” It depends on variables like quantity, quality and cost. David Kazmer, Professor of Plastics Engineering at the University of Massachusetts Lowell, said in a published paper that 3D printing currently makes sense for the most rapid “procurement time to quantity” for a small quantity of 50 or fewer units.
So for production runs, injection molding is still the best manufacturing method, especially considering the long production time involved for 3D printing compared to injection molding. There is an emerging “hybrid” practice of 3D printing the mold tooling inserts only, then producing the parts with injection molding.