FWIW, my current host is Toomim Brothers, which I'd say is fairly authoritative on the subject, and their opinion was that "Yes, the A2 Terminators are very heavy. The steel they use for the case is much thicker than necessary, and the aluminum heatsinks are also larger than needed. If they had a better design, they could be a quarter the weight and an eighth the size."

Jonathan also elaborated on the 10% power difference:
"There is a lot of variation in how silicon gets doped during the etching and doping processes of making transistors. As there are two types of transistors on a CMOS silicon chip (n-channel and p-channel MOSFETs, depending on whether the dominant charge carrier is negatively or positively charged), there are two separate dimensions for how much doping a chip can have. More doping results in faster chips that have more leakage current. Less doping results in slower chips with low leakage current, but which might need more voltage. The speed of the N and P MOSFETs can be described as a position on a rectangle, and placement in some of the corners results in worse performance or energy usage than others."