What is the Centurion's speed compared to the other ground vehicles that use Anvil's Atlas Platform (Ballista and Spartan)?
Cloud Imperium
Due to the higher mass of the weapon system and extra components, the Centurion is slightly slower than the Ballista. In the future, the Ballista will have the "benefit" of reduced mass when its ordnance is depleted, so will gain improved speed and handling when out of ammunition.
starfarer.space · Q&A: Anvil Centurion