Back then (https://spacey.space/@astrodad/113836864029804066) I mentioned Cyclical development, which is the advantage SpaceX had - being able to fly paying missions, push the envelope of the hardware, improve reliability and process efficiency. I kinda meant iterative as well, but:
One of the problems with SLS is that the flights are so few and far between, the support teams and engineers can't learn from each mission to improve the next. Hopefully Blue Origin can find a happy medium between those two approaches.