The difference between Digg and Slashdot is that with Slashdot, all the stories were placed by editors. You might have been able to submit stories to the editors, but there was no upvoting and the front page was purely up to the editors. Of course, later Slashdot added Firehose, and then awhile after that I stopped reading Slashdot.

Slashdot had moderation for comments, but no similar mechanism for stories. Digg had the voting system for stories and for comments.