The switch between the two happened because my job responsibilities changed, and Org-mode is better at supporting my current role as a team lead and developer. Taskwarrior was better when I was only developing software. Personally, I feel this says something about what usage patterns the two are best for.
As a developer, I spent almost all my time in a terminal. Taskwarrior (plus a few shell aliases) allowed me to create tasks the moment I thought of them. I could then get back to work and see the task list later. Switching to Emacs every time I needed to create a task would have been unproductive and I probably would not have done that.
As a team lead, I spend most of my day researching, helping out team mates, building product road maps, etc. I spend time in the terminal, but not as frequently as before. And I'm not developing as much either, which means I can now take the time to switch to Emacs, capture a task or thought in Org-mode along with any details, and then get back to it later.
My perspective on the two: - Taskwarrior never gets in your way. It takes a few seconds to record a task and then get back to what you were doing. But you end up not recording many details about the task, mostly it's just the title. Great for small bugs fixes or development tasks that come up while your developing. - Org-mode is great when you want to record details for the tasks you are recording, take notes, and just generally write anything with details.
Hope this helps.
Taskwarrior is probably a fine piece of software though.
Taskwarrior looks like it can work better "out of the box" and definitely more useful for someone who isn't Emacs-proficient.
Org-mode, for better or worse, is flexible enough to support lots of different kinds of workflow. It's cool if you know what you want to do, and the defaults will be enough for simple GTD workflow, but if you aren't sure how to properly organize yourself, you'll find yourself searching a lot for ideas from other people.
My current org-mode config looks like this: https://github.com/TeMPOraL/conffiles/blob/master/emacs26/.e....
You can think there's lots of stuff in it, but frankly, this is mostly on the lower end :). Most of the code is for tweaking tasks, clocking and agenda views to better fit my workflow. It's by no means finished - living in org-mode is very much about slowly discovering your ideal workflow and molding Emacs around it :).
Well, I use Orgzly on my phone, but I use emacs on my desktop & laptops. Orgzly is okay, but not great — and it has some weird bugs. It's definitely not a complete port of Org mode, or even a port of most of Org mode. For what it is, though, it's better than nothing — and better than the current alternatives.
I really wish that there were a good touch-aware port of emacs on Android.