From the Boeing web site
The 747-8 is the only jetliner in the 400- to 500-seat market, stretched 5.6 m (18.3 ft) from the 747-400 to provide 467 seats in a three-class configuration and a 14,815-km (8,000-nmi) range. Using 787-technology engines, the airplane will be quieter, produce lower emissions, and achieve better fuel economy than any competing jetliner.
Operating economics will offer a significant improvement over the A380.
The 747-8 is more than 10 percent lighter per seat than the A380 and will consume 11 percent less fuel per passenger than the 555-seat airplane.
That translates into a trip-cost reduction of 19 percent and a seat-mile cost reduction of more than 4 percent, compared to the A380.
The 747-8 can use the existing infrastructure and ground equipment at most airports worldwide.