Elliott, Trello.com is Kanban while Fluxes.com is to-do lists/checklists. Some people find kanban more convenient while others find lists more convenient. Fluxes is comparable to Asana, but unlike Asana, Fluxes is completely free.
For example, if you have a list which consists of 8 tasks, on Fluxes you can create a checklist and assign different users to different tasks, with each task having different deadlines (and each task having its separate section for discussions).
Then you can copy that list with a couple of clicks, even with assigned people and files, if your team should repeat the same workflow.
How would you do this on Trello? On Trello you can create a checklist inside a card, but tasks in that checklist can't have different deadlines or separate discussions, or people assigned to each separately. So you would need to create different cards. But if you want to copy the same sequence of 8 tasks, in this case you would need to copy 8 cards and manage each card separately and that is not a couple of clicks. Just one example.
So, which tool to use totally depends on your work processes and how you prefer to work. I don't think it's bad to have a lot of useful free tools to choose from.
Cheers!