Smoother running or higher RPM when the choke is on usually means the air/fuel mixture is incorrect. The engine should run strong and smooth when the choke OFF and the throttle in FAST. There are two reasons it runs "Better" when the choke on: (a) not enough fuel is getting through [partially blocked main jet or emulsion tube, dirt/debris in carburetor) or (b) vacuum leak (bad carb gasket/seal).
Since it is a new mower, a dealer should have a look. If it is determined to be a factory defect, Honda will cover the costs of repairs. But, if it's dirt/gunk in the carburetor, it's not a factory defect, and you'd be responsible for repair costs. The good news even a brand new carb is generally < $30. You can find a Honda dealer here:
[url]http://powerequipment.honda.com/dealer-locator[/URL]