When comparing Toodledo vs Turtl, the Slant community recommends Turtl for most people. In the question“What are the best cross-platform task apps?” Turtl is ranked 15th while Toodledo is ranked 23rd. The most important reason people chose Turtl is:
Turtl has applications for all the major operating systems, as well as Android. In addition, there are extensions available for Firefox and Chrome that cooperate with the downloadable applications.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Can create to-do items via email
It's possible to create a to-do item by sending or forwarding an email.
Pro Decent filtering and sorting
Pro Priority organizing
Pro Great GTD implementation
The GTD principles are very perfectly supported by Toodledo.
Pro Functionality-rich
Integrated sharing, note taking, habit tracking, and outlining make this a more powerful tool than a simple list of to-dos.
Pro Upload From CSV
Quickly upload an excel (CSV) file template of tasks to a folder for complex but repeating projects.
Pro Well documented, free-to-use JSON API
If you adopt Toodledo as your productivity system, you can be confident that you can extend it to fit your needs with this programmatic access.
Pro Can tag items
Pro Space to add lengthy text
Notes area that can then be hidden.

Pro Sends a daily email reminder
Toodledo reminds you via email of the tasks on your plate for the day.
Pro Apple Watch support
Integrated support for Apple Watch lets you check on your to-dos on the run.
Pro Multiple Platforms (Windows, Linux, macOS, Android, Firefox, Chrome)
Turtl has applications for all the major operating systems, as well as Android. In addition, there are extensions available for Firefox and Chrome that cooperate with the downloadable applications.
Pro Open source
The app is licensed under GPLv3 making it open source. This means that anyone can use the code and contribute. This also makes it easy to use on one's own server or for company solutions.
Pro Good security
After assigning a password to your account in Turtl, a key is created to encrypt the entire account. No data is stored on their servers meaning they have no access to unencrypted content. This is a huge leg up when comparing to other Evernote alternatives.
Cons
Con Free version limited to 20 folders
Con Android app has annoying notifications
Whenever the app fails a background sync action for any reason (server issues, lack of internet connection, etc.), a notification appears.
Con Good as a starting point
Toodledo is a good starting point, but is essentially the same as an Excel spreadsheet where you have to build your workflow via the saved searches.
Con No iOS app
While many other operating systems have a client, iOS does not have one yet (though it is planned).
Con No image embedding
Instead of image embeddings, there's a sort of poor man's substitute: image + description. If you add an image, you can create a description of any size and with all the formatting features. It can be used instead of image embedding but much more limited: only one image and only at the very top.
Con Internet dependent
Requires Internet connection to initiate offline mode, loses access to notes without Internet or server.
