I also believe that the ZW-L only has one plug, so to get 4 outputs with a PowerMaster setup you'd need 4 PowerMasters each with it's own transformer and thus 4 plugs. Now the ZW-C on the other hand is more like a PowerMaster in that each channel can take a transformer so that'd be 4 plugs if you wanted max rating, otherwise you can share one transformer with all 4 outputs.
Like stated above, the ZW has handles, and as a conventional guy I'd pick it because of that.