Sanyos are great panels, especially in hot locations. Still they cost more than regular panels. The efficiency has to be balanced against the cost and the life of the panels. Figure that panels will last 30 years and the upfront cost doesn't seem to big. And many states base their rebates on panel efficiency so the Sanyos qualify for more rebate upfront too.
i agree with solar boy, efficiency and cost, must be balanced. To be very honest, there are too many companies producing solar panels. Efficiency for mono cell solar panels normally is above 16%(leader in the market at 17.3%). Most companies can guarantee a 25yr life span. What is left is the price and your personal preference.
from what i know, US end users are paying like USD$5/W, but china companies are selling at USD$2/W. Difference? Not much. then why the price difference? labor cost, and maybe the solar panel has already changed hands many times. But advantage of paying $3 more per watt? More efficient after-sales service due to distance.