Having done DARPA contracts, the difference I saw is that they feel more like moonshots. They are more fun to work on because you're encouraged to let your imagination run wild. Since failure is almost guaranteed it is kinda liberating since you don't feel the pressure to avoid failure. Failure IS the process here. Working on a DARPA contract is really the space where "there's no dumb ideas." Of course there actually are, but there's much more freedom to suggest these because at worse you rule some things out. And often the dumb ideas lead to good ideas that haven't been seen because the path starts at something that is clearly absurd. But then again, the premise of the problem is absurd so you have to try absurd things.