We recently saw waterfall versus agile in actual rockets

Blue Origin spent years meticulously designing their rocket. They tested it on the ground. On the first flight it got to orbit, but the first stage exploded while re-entering

SpaceX started building their rocket out of carbon fibre. Changed to stainless steel. Started flying subscale demos, flew high altitude full scale examples to find if their aerodynamics was right, and haven’t actually tried for orbit yet

Blue Origin is trying for a last generation rocket (where the first stage is recovered) but bigger, SpaceX is trying to create the next generation where both stages are recovered