The biggest issue is power supply. If you are on 30amp, running the roof mounted and the portable is likely overloading the system. Don't be surprised when your power cord has burnt ends. If you have 50amp, it shouldn't be a problem or if you run a separate powerline from the pedestal (but then you need a way to get it inside.
The dual hose units cost more but are more effective than the single hose units. The single hose units use cooled interior air to cool the condenser and then pump it outside. This means it pulls hot outside air into the RV to replace the air pumped out. Yes, it still cools but not as efficiently. The dual hose units pull outside air in to cool the condenser.