Sidequest for Slack VS LetsDo.io

Sidequest creates helpdesks and task ticket queues entirely inside Slack, combining the best features of helpdesk systems and modern task managers.

Let’s Do is a Slack app that gives you a to-do manager within Slack. You can set due dates, assign tasks and share lists of to-dos with your team. With the app, each channel in your Slack workspace becomes a to-do list easily accessed by the channel members.

The app can be used as your primary task manager, as a complement to an existing task management solution, or to design your own processes around to-dos. It also supports personal to-dos, which are your private to-dos only visible to you.