When comparing Emacs Org-mode vs Nozbe, the Slant community recommends Emacs Org-mode for most people. In the question“What are the best cross-platform task apps?” Emacs Org-mode is ranked 3rd while Nozbe is ranked 35th. The most important reason people chose Emacs Org-mode is:
This app's flexibility is based on its minimalist approach, giving the user near-infinite freedom.
Specs
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Pros

Pro Ultimate flexibility
This app's flexibility is based on its minimalist approach, giving the user near-infinite freedom.
Pro Absolutely free
Emacs with Org-mode is free as in beer and free as in speech – that is, it costs nothing and it’s totally open source.

Pro Files are usable anywhere at anytime
Users are not tied to one service provider, program, platform, or database engine.

Pro Incredibly extensible
There are many plug-ins for Org-mode, including Org-habits and Org-notify. If Org-mode lacks some piece of functionality, it is very easy to add it.
Pro Agenda views
Pro Excellent unofficial Android app (orgzly)

Pro Offline support
Pro Efficient features for deadline organization
Pro Supports plaintext spreadsheets
Pro There are a lot of extensions, for exporting to html, bootstrap, js-reveal and much more
Pro Quickly add rich text
Pro Cross-platform
With Nozbe you can manage and get your tasks done anytime and anywhere. Nozbe has apps for iOS, Android, Windows Phone, OS X, Windows, and Linux, as well as a universal web interface. The sync works smoothly and handles off-line work responsively – all the work saved on your device will be synced to the servers as soon as you’re back online.
Pro Great real-time team collaboration features
Nozbe can be a perfect tool to manage communication, data, and workflow for teams – large and small. Features like comments, @mentions, admin/guest roles, attachments, and categories are great for managing all the documents and emails associated with a project. You can also invite people who don't have Nozbe account to participate in your projects.
Pro Nice and simple user interface
Nozbe is based on Getting Things Done (GTD), a productivity philosophy created by David Allen. However, you don't need to know the methodology to use the tool. You can just add projects, tasks, and attachments, and gradually learn to use the other features to organize your time even better.
Pro Practical integrations with some favorite tools
Nozbe integrates with email, Evernote, Dropbox, Google Drive, Box, Google Calendar, etc.
Pro Nozbe.HOW templates
Nozbe users curate a vast collection of free templates that share everything from favorite recipes to tried-and-true vacation itineraries.
Pro Highly intuitive and works the same way across all platforms
Cons
Con Unintuitive user interface
The key combinations are unintuitive and difficult to remember. This is probably because there are a lot of hidden "modes" depending on where the cursor is. Actions aren't paired with reversing actions like in other todo apps. For example, hitting shift-tab does NOT reverse the effect of hitting tab.


Con Android app isn't very good
There are several user-created apps for Android, but none seem to offer the same level of functionality as other to-do apps.
Con Not really cross platform
Although it is possible to get a lot of it working, no all in one, sync included, out of the box solution is available for mobile devices.
Con By default, a hard-to-read display
The default way of writing an outline or checklist creates a very messy wall of text that's difficult to read with no vertical spacing. You can manually add vertical spacing, but the Org operations don't preserve it. There are pretty-display modes, but you need to remember how to enable them, etc. etc.
Con Limited free plan
After the free trial you can choose to remain on a free plan, but you’ll be restricted to a max of 5 projects and will have limitations on collaboration.
Con Task dependencies missing
Nozbe is great, but one shortcoming relates to "task dependencies" in projects. You should be able to sequence your tasks so that, when you complete a task, the next one that needs to be done becomes the "priority" task for that project. This is a vital feature that will make the program dramatically more useful. The company claims to be working on this improvement.
