Surprisingly the Jazz can actually hold more cargo than the Mazda 3 hatchback even with it's size.

Specs
Mazda 3 hatchback w/ seats up 17.1 cubic feet w/ seats folded 31.2
passenger volume 95.4 cubic feet.

Honda Jazz w/ seats up 21.3 cubic feet w/ seats folded 41.9
passenger volume 90.0 cubic feet

If you feel that you will carry cargo more than people then the Jazz may be better along with it's fuel economy. But if you value passenger space more than cargo capacity along with driving feel then the Mazda 3 is the better vehicle.