A sintered base CAN be faster if you habitually wax it properly. A poorly maintained sintered base is quite slow, on par with extruded.  You remember the Dew Tour stop last year when LJ borrowed a pair of Armada skis because conditions were so sticky that his extruded base Lines caused him to be too slow and come up short on landings?
An extruded base really is not comparable with a properly maintained sintered base. And a normal sintered base does not compare to a race quality sintered base. Race bases use the highest grade base material you can get, which when maintained properly is much faster than a normal sintered base.  A real race base is honestly not used on park skis. When companies say "race base" they usually mean a nice sintered base, still better than normal sintered but not true world cup level quality.