Trello is really great compared with your average todo list, Excel spreadsheet, or planning tool. Unless your needs are super complex or your list of tasks is longer than a few hundred items, I'd say start with Trello until you need something else. If you're in a domain where there's good planning tools or you're tracking a ton of items, e.g. issue tracking for software development, then it's worth doing a more detailed evaluation of alternatives for you.