One thing I learned from a recent Everyday Astronaut video is that NASA has a long history of trying to calculate the chances of failure for a vehicle before it

One thing I learned from a recent Everyday Astronaut video is that NASA has a long history of trying to calculate the chances of failure for a vehicle before it has ever flown. They got it wrong with the space shuttle for example. And this method requires a lot of extra factors of safety and expensive parts. An alternate method is to test in flight, and this is what SpaceX does. Boeing uses the other method. So Boeing systems are supposed to be relatively failure free, while some SpaceX systems may at some point be expected to fail. Of course SpaceX is supposed to have their testing done before humans get onboard, so those systems should still be reliable. But a big difference is Boeing tests on the ground and SpaceX tests in flight.