i think both are equal with the operating costs BUT think that eventually the 747-8, although it was launched way more later, will sell better than the A380 does... this because of the following reasons:
-lower operating cost, as well as per seat as per trip cost
-newer technology used.. that from the 787
-lower maintenance cost, because its based on the 787 wich will be revelutionary in maintenance time needed
-compability with 747-400, it doesn't require more than a couple of hours of training to train a pilot from a 747-400 to an 747-8 , and also ground equipment doesn't need special requirements.
-the 747-8 is able to fly to over 220 airports, while the A380 makes it to about 30 airports
- airlines like BA
, wich they said themself, are seeying the 747-8 capicity as a better number of seats than the A380 has.
A380 is a package freighter, while the 747-8 can take lots more heavy cargo and more bigger containers thanks to its quite impresive stretch
although the 747-8 has a lot more advantages, the A380 also has some advantages
-is already available in end 2006, while the 747-8 is available in end 2009 at earliest
- takes more people, so for airlines like Qantas , wich fly's the busy SYD
route is more atractive
-offers more space for Things like a bar or massage room