As per Magento standard, the second option is right to add a new record to an entity using the repository.

If you want to update exist then you have to load the record by a primary key using getById()

$slider = $this->sliderDataFactory->create()->load('PKID');

$this->sliderRepository->save($slider);

As per Magento standard, the second option is right to add a new record to an entity using the repository.

If you want to update exist then you have to load the record by a primary key using getById()

$slider = $this->sliderRepository->getById('PKID');

$this->sliderRepository->save($slider);