There are times when I need to arrange a meeting and invite multiple users. I want to notify them so I need to assign to teams. I also want it to be neat and organized.
If I use tasks I’ll be able to assign to teams, but it will be messy, with many duplicated tasks in my list.
If I use sub-task, everything will be nested in a single task. It will be clean, in one place, but I’ll have to remember everyone in a team(s) and key-in one by one.
I now have a semi-solution.
First do the first method; use the task and assign to teams. Then when you have all the duplicated tasks, click on the one you want to keep as parent task. For the rest, you drag and drop them into this task. It will be sub-tasks inside. Wha-lah, now you have what you want. Both, the simplicity of assigning tasks to teams and keep you list neat.
Wait, but I said semi-solution didn’t I.
The bad news is, you have to drag and drop tasks one by one. 
Please, please, please, the ability to move multiple tasks to be sub-tasks in a task at once.
Either that or sub-task with ability to assign to teams.
Sub tasks is good but you have got to fix many things with it seriously, especially UI.