It is all about head height (the actual waterflow at the destination)
and energy conservation. There are plenty of postings you can search
for that can help you find the energy savings. Make sure you compare
apples to apples. Get all of the pumps you are looking at into the
same measurement. I found watts to be the easiest. If you google
this news group you can find out how to get amps to watts and other
helpful info. Here is a link to a site that breaks it down into
waterhorsepower which is another way of comparing pumps.

http://www.moneysaverpumps.com/CPI.htm

The CPI equation does the whole amps to watts, considers 115 volt and
230 volts and considers the loss of flow based on head height into the
equation. There is a chart further down on this page that has
superfalls listed in it...

Good luck.