No real advantage or disadvantage I'd say, unless it's below freezing out. I suppose in theory the less piping that has pressurized water flowing to it the lower the chances of a leak, but the even better plan there is to just turn the pump off when towing.
The valves are really just there so you can isolate them in below-freezing weather. Otherwise the shower becomes sort of a weak point in terms of freezing, since it goes outside the insulation.