Here is a top level treatment on the differences between the two nav units: http://www.wk2jeeps.com/wk2_navigation.htm
Personally, I think that the 730N is a better device. The speed display screen is missing, but then, you do have two other speedometers in your vehicle.
Just to further what berk483 mentioned: the 430N uses an external uconnect module whereas the 730N has uconnect built in. A conversion harness is required to mate the 430N-uconnect-module type vehicle harness in your vehicle to the 730N. This is detailed on the bottom of the page linked above.
There is, then, also the issue of adapting the other vehicle to the 730N. And, finally, your 730N is likely to be secured with an anti-theft feature that will trip when moved to another vehicle/VIN.