The two basic sump pump models are upright (commonly called a
pedestal) and submersible. Either will work well with proper
maintenance.
The pedestal pump has the motor on top of the pedestal and the

pump at the base, which sits on the bottom of the sump. The
motor is not meant to get wet. The pump is turned on and off by
a ball float. One advantage of this type of pump is that the on/off
switch is visible so the action of the ball float can be easily seen.
Submersible pumps are designed to be entirely submerged in water and
sit on the bottom of the sump well. It is activated by either a ball float connected to an internal pressure switch or a sealed, adjustable, mercury-activated float switch. The sealed mercury switch generally is more reliable
than a pressure switch. Submersible pumps are quieter than their pedestal cousins.
A battery operated backup pump in the well is essential. It serves a purpose in three situations; back-up in case of failure of the main pump, support if the main pump cannot keep up with the incoming flow of water and of course, the only working pump during a power failure. A good backup pump will sound an alarm to notify you that it is assisting or has taken over the water removal.
Newest to the market are "Intelligent" sump pumps, with built in backups and notification systems, that automatically email and call if there is a failure. This could be a valuable, stress relieving solution for vacationers. If there were an Olympic event for sump pumps, these babies would be coming home with the gold (and our rabbit could hang up her water wings for good).