I suppose that was my point - the A380 has 4 engines and much more space than even a stretched 777 will have, so the idea of those two competing is a bit weird IMHO.
I was very surprised to learn below the decks, the 777-300ER has a larger cargo area than the A380 and most operators of the two aircraft report higher revenue cargo numbers ($) for the twin compared to big bird.
I was told the 777 not only begins with a larger volume below, but once baggage is loaded on both aircraft, the A380's volume is further lessened in comparison.
One final note to share - the amount of "belly" space utilized fleet-wide adds up to around 40% of the global air cargo market.