There is a whole Forum Post about ProfileService
Basically:
ProfileService is a module that basically helps with preventing Data Loss, and allows you to do a lot more than DataStore2
It can also work or “Massive” Projects.
DataStoreService is just DataStoreService
It just Gets and Saves Data, while having Data Loss sometimes, the ProfileService module basically just helps with Data Protection, Data loss Prevention.
Personally I prefer to just use DataStoreService
I rather make my own systems.