When comparing Amazing Marvin vs Momentum, the Slant community recommends Momentum for most people. In the question“What are the best cross-platform task apps?” Momentum is ranked 34th while Amazing Marvin is ranked 51st.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro GTD
Pro Works excellently on Linux
With just clicking the right button of the mouse, entering properties and giving write and read permissions and clicking on the "Allow the file to run as a program" box is installed with total ease.
Pro Great support
Pro Active development
Pro Specifically designed for GTD
Pro Automated Next Steps
Next steps have a separate view. Tasks can be updated sequentially or parallel.
Pro Projects and Tasks can be endlessly nested
You can nest multiple projects with tasks, there is no limit.
Pro Has an offline mode
No permanent internet connection needed.
Pro Cross-platform
Web-based, progressive-web-app (PWA).
Pro Realtime synch
Data instantly updates on all devices.
Pro Clean design
Lots of space helps focus on the tasks.
Cons
Con Not free
Con Beta interface is confusing for first-timers
The interface is very opinionated (this is a good thing). But it is not obvious how to map user's own GTD variant onto the one the author has in mind. Maybe after it is in production, there will be better on-boarding.