The noise of the generator is measured in Decibels at a distance of 21 feet (or 7 meters). Decibels are logarithmic, so the difference between 50 and 60 is much more to the human ear than the difference
Figures are fuel consumption values at 100% (full) load. It is unlikely that the generator would run at full load for an extended period of time. Therefore, your consumption would decrease accordingly.