First look comparison:
•User interface on the first look looks very similar and can both of them does similar things. •Both are based on Kanban board where bucket of Tasks can be created and check list, attachments etc can be added
Planner Trello
Task creation:
•Trello and Planner •Task creation method creation is very similar in both Trello and Planner with ability to create checklist, attachments, due dates, description etc
•User assignment: In both a task can be assigned to more than one users
•Checklist: Trello can have more than one Checklist in a Task and checklist item can be assigned to a person whereas Planner can have one checklist and cannot be assigned to someone. –Checklist is visible in card in Planner but not in Trello
•Notification and tracking: Task notification are recieved by emails and activity feed in Planner whereas Trello has activity feed in the card itself and emails are sent to assigned users
•Filter: Planner seems to have more option to filter and create views for Tasks
•Other options: Trello has more options such as make template out of a task, watch etc but has some items such as copy , move same as Planner
Planner Task creation Trello Task Creation
Calendar View:
•Calendar view works more or less same except following points:
- Planner has both start and end date while Trello only has Due date
- Planner calendar can be viewed in Outlook as well while Trello calendar can be added as iCalendar
- Planner also shows tasks on side if not assigned a date while Trello does not
- In Trello Calendar view is not available by default and needs to be added as ”Power Up”
Planner Calendar view Trello Calendar view
Progress view:
Planner has progress view but Trello does not have by default

Summary:
- Trello and Planner work in very similar way
- In comparison both have some plus and negative points but in broad level both can work in same way
- It should not be extremely difficult to adpat to Planner if you are using Trello
- If someone is paying extra license fee for Trello then maybe Planner is more suitable option if you have O365 license.
Connect with me on Twitter or Linked In if you need more information.
Subscribe to my YouTube channel
https://www.youtube.com/channel/UC6vLzWN-3aFG8dgTgEOlx5g
References:
https://www.microsoft.com/en-gb/microsoft-365/business/task-management-software