The wide wheelbase reduces the load on the pavement. I just checked it now, using the bogie undercarriage for a C141 which I have in my design system. Extending the wheelbase by 300mm from the standard 1427mm to 1727mm dropped the ACN on a ‘D’ subgrade from 66 to 59. The effect is less on stronger subgrades. (A/c weight 142.9 tonnes).
Airbus have a three-pronged main undercarriage design philosophy encompassing both four- and six-wheel bogies to ensure it can keep the pavement loading within limits. The A350-800 and A350-900 will both have four-wheel bogies, although the -800's will be slightly shorter to save weight. Both will fit in the same 4.1 m (13 ft) long bay. The proposed higher weight variant, the A350-1000 and the A350-900R will use a six-wheel bogey, with a 4.7 m (15 ft) undercarriage baytrack.
The Comet weighed 50-71 tonnes, and the A350 weighs 259-308 tonnes, so the Airbus people have a lot more weight to contend with.