Here is an actual test run that took 14:57 on Monterey and 4:30 on Mavericks.
I used SuperDuper! to backup a USB 3 drive containing 567.66Gb of data, where one file of about 10Gb had been added and one deleted, to a sparsebundle on a different drive. SD! scans the source and only makes changes to the destination, so there was about 20Gb of change and another 550Gb of scan. The source has to be read by the computer and the changes written to the destination. There is a small amount of time required to mount the sparsebundle on the destination drive.
The Monterey system, a 2021 16Gb M1 MBP, consisted of a Thunderbird 3 to USB 3 adapter connected to a USB 3 hub to which two USB 3 drives, the source and the destination, were attached.
The Mavericks system, a 2012 16Gb Mac Mini, consisted of a USB 3 hub to which the USB 3 drive was attached as the source, and a Firewire 800 connected to a Drobo as the destination.
I believe the newer system should have been faster, not 3X slower. The big differences were, of course, the computers/operating systems plus the Thunderbolt 3 to USB 3 adapter cable. Both hubs have been used on the Mavericks computer at one time or another and there is no real difference there.