Hi
I've been wondering what ambient temperature the various designs were tested at.
It's certainly true that trying to maintain a big temperature difference between inside and out will use more power than a small difference.
In most of Europe typical daytime temperatures will average around 14 Celsius (57 F) getting down to 5 C (41F) or below at night.
Normal seasonal variations apply, of course, but higher Summer temps will be balanced out by significantly lower Winter ones. Generally, people don't heat their kitchens at night, so most fridge compressors get a significant rest at night, because the cabinet temperature matches room temperature.
Is this true for America? Remember the testers will have to allow for a person living in Texas, measuring his power consumption, looking for an excuse to demand a refund!
I never take the figures quoted by manufacturers at face value.
As others have already stated, motors will tend to run a little faster on 60Hz, but the higher frequency will not take the coil (inductor, to give it it's proper name) as close to saturation so I would expect it to consume a little less power. In other words, I think the 50Hz motor running on 60Hz is probably safer than the other way about, though obviously there are no guarantees once you go outside the manufacturers specifications.
Be careful of anything with a clock, or timer in it, however. Many of these use the line frequency to sync their clocks, so they may run 20% fast...
sparks