The all in one! The Premier Alpha series integrates a basket-type pre-filter and self-priming capabilities into one efficient package for trouble free operation.
Since an internal diffuser allows for displacement of trapped air, this type of pump will continue to move water even when there is some air in the line.
The integrated strainer basket on all the primer units helps protect the internal rotating parts of the pump, i.e. branches, leaves, etc.
The simple cover allows for quick cleaning and replacement.
Because the unit can operate for short periods of time without full water flow, it provides a small cushion of comfort to the owners of those systems where the water level drops below the intake point. 

Motor is totally-enclosed, fan-cooled for durability.