Powered vs Parachute Landings
SpaceX planned on extending 4 legs through the heat shield and using the Super Dracos to fly a powered descent, with parachute backup. NASA, understandably, was concerned that poking 4 holes through the heat shield was not a proven procedure, and a powered landing vs parachute was a radical departure from the norm. So, if SpaceX was willing to invest a billion or so on their own dime and possibly delay the Crew Dragon, they could do it. SpaceX wisely backed down and changed over to parachutes and water.
Boeing all along designed their Starliner capsule to have impact-cushioning bags and not interfere with the heat shield, so since the Russians had done it forever, NASA said it was OK to proceed. SpaceX was too far along with Dragon to redesign to include impact bags, so they stayed with water landings.