I believe the HR-V has the same 1.5L engine and drivetrain to that of the Jazz, but in a larger more expensive package.
The HR-V looks more premium as well, but offers little in technology to its smaller Jazz cousin.
It all comes down to looks and slightly higher specification, but you have pay a lot more for it.
I didnt need a larger vehicle, and the sole reason i bought a Jazz, was because of its legendary reliability.
I didn't buy the Jazz because its a looker, i bought it because of its reputation and because the car was almost £7000 below list price.
Im so impressed with the car, that im definitely getting another when the time comes to change.