When comparing Priority Matrix 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 Priority Matrix is ranked 47th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Helps prioritize, rather than simply listing tasks
Priority Matrix helps me focus on what's truly important on my todo list, so I can work more efficiently.
Pro Super easy to share / delegate tasks
All I have to do is press a button, rather than drafting a whole email to one of my co-workers.
Pro Solid methodology
The software implements time proven methodologies; not just a to-do list.
Pro Lots of different views
Priority Matrix makes it really easy to see your task list in different ways: You can see it in the quadrant view, calendar view, a filterable list, and also a Gantt Chart if you have the business license.
Full disclosure: Originally posted by an Appfluence Intern (who was equally impressed with the software's layout and functionality before working there)
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 Expensive
Used to be free, is now $12+ a month.
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.