This is a bit of a shortcut answer -- I hope you will forgive me, but after many trials and failures (these pool cleaners are expensive!) -- I have found the Polaris 360 is a proven workhorse. It never breaks.
- If you want to avoid buying a new cleaner every other year ($500+ a pop), buy the 360. I have had mine for at least 5 years and only replaced bags, hose, and tail foam.
- I am not sure about the energy deal, but considering how the 360 has lasted, the energy difference is not comparable.
- I will add one more thing, and that is it really vacuums. Therefore, one hour of running time is all you need. A lesser performer might require a longer running time, thus using more energy at the pump.
Don't be tempted to buy the one with more bells and whistles. The Polaris 360 is all you need.
For more information:
Read Lee Hall's Q&A "Does anyone know the best way to manage a pool ecologically?"
Read Cassandra Adams's Q&A "Is limestone tile a sustainable choice for a pool and patio surface?"