I've always thought it was the multiple account management features. I personally as individual manage multiple accounts just running groups/orgs I do on the side. In addition my whole team shares the work of watching our Company account and replying/providing-content.

Schedule tweets are definitely awesome, we certainly are not using them enough. I assumed Companies like Buffer would be more specialized at that use case and had been meaning to check them out for that. Guess I should actually try what Hootsuite has built in.