While Bell’s rival V-280 uses tiltrotor technology, proven in widespread service on the V-22 Osprey since 2007, the Defiant uses Sikorsky’s revolutionary compound helicopter technology, which promises superior agility — but which has only actually flown in two experimental aircraft, the X2 and S-97 Raider, both of which are much smaller than Defiant.

Sikorsky and Boeing are saying that their aircraft is taking longer than Bell’s because their design is more inventive — harder, riskier, and more time-consuming, yes, but ultimately better. In particular, while the SB>1 looks like it’ll be a little slower than the V-280, going by the companies’ projections for top speed, Sikorsky and Boeing say their machine will be much more maneuverable.