The reason for marketing the same drug under two different names may actually have nothing to do with psychology.
Many insurance companies do not cover prescription drugs to aid one in quitting smoking (which is silly considering that quitting improves your health and reduces their costs) but they do cover prescription drugs used against depression.
Using two different names for the same drug allows the insurance company to determine whether to pay for the prescription or not.
For that reason some smokers ask their doctor to prescribe Wellbutrin instead of Zyban. Of course, technically, they are committing insurance fraud.