A lot depends on whether you want to emphasize the project planning or the project execution side of things.
Planning is about generating views on the data (data => information on the project) that make sense in the design phase. Design is a batch activity: when it's done, the generated design sits there for further consultation. This means that the planner has near to total latitude in choosing whatever tool she like, because the need for coordination with others is minimal. The spreadsheet has proven to be far and away the most valuable planning tool, at least for us. Every Edgeryders project as at least some back-of-the-envelope allocation of resources on a spreadsheet. In some cases, we are required to build Gantt or PERT charts.
Execution requires tighter coordination, hence some kind of management. I see Dynalist as a management tool, not a planning one:
- It is a management tool because it breaks down the project into a to-do list, with native support for personal to-do-lists. Each person can simply work through their own to-do list as created by management; no need for a big picture view of the project, at least in principle.
- It is not a planning tool because just seeing the list does not intuitively resolve into a bird's eye view of the project. It does not support computation (like spreadsheets) not visualization (like GanttProject or similar).
Dynalist is attractively simple and no-nonsense. But, at least to me, it's barely fit for purpose as long as it does not support notifications.
Trello, as I see it, attempts to be both. Its metaphor for the planning function is the notice board. The idea is that seeing your project lined out as a set of re-arrangeable virtual post-its will help you think about it.
In my own opinion, this metaphor is weak. It does not add any information to just writing things down in Google Doc, or a piece of paper. Others like it.
On the execution side, my experience is underwhelming. I have never been part of a team that was able to actually use it. The normal pattern is this: someone proposes it as a tool, people accept, the board is created but then not maintained. Trello requires a very disciplined team, with tight coordination. I used other tools with similar issues: they give you an integrated environment with tasks, notices, chat, everything commentable. To make the most of it, you need to be on it hours a day. I suspect they were designed with high-effort intensity projects in mind: complicated software development ones. People are working 8-10 hours per day on the project, and so they work with the environment always open. It helps that they have bosses, and they are not allowed to opt out. This was my contribution to the ongoing search for a tool: it has to be dead simple and lightweight.
But this, I repeat, only applies to management tools, which need to be shared across whole teams. When you design you are mostly alone, you do not need to coordinate (much), so you are quite free to choose what you want.