Indeed, they do the same job. The following is shallow and brief:
DiffUtil over SortedList is a matter of circumstances, wither your existing data listing implementation allows you to easily switch to SortedList or keep it and only improve it with DiffUtil. Calls on adapter are simplified out of the box, just one line. Definitely, less code, for the lazy people.
SortedList gives you more granular control to entire add, remove, update (ARU) process, like batching ARU operations in same transaction.
I’m so indecisive. ☺