Randy
I'd like to add to what others have said, The horizontal sumps [both carburetor and fuel injection] will not allow any pooled fuel to drain out the servo or carburetor. This issue can happen with any landing gear arrangement. However, more fuel tends to pool into the rear of these sumps on conventional gear aircraft.
Without the sniffle valve, you may get a fuel back fire on the ensuing start up. The back fire can damage a number of components on the engine.
Charlie Kuss