When comparing Things 2 vs Nirvanahq, the Slant community recommends Nirvanahq for most people. In the question“What are the best GTD apps?” Nirvanahq is ranked 3rd while Things 2 is ranked 15th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Cloud sync
Users need to create an account for Things Cloud (the account can be created from any device). Once signed up, cloud sync will be active, and you’ll have to login on all of your devices to complete setup. From that point on, syncing happens in the background. It is invisible and always reliable.
Pro Daily review
At the beginning of every day, a yellow box appears at the top of the Today section, displaying all tasks scheduled for this day. You can investigate them, and then decide which ones you’ll have for that day and which one you’d rather want to delay.
Pro Easy to set up and use
Things 2 works from the moment you start it up. Simply add a task and when you want it done by. You can also add notes to tasks or tag when you need them. Things allows you to quickly and easily start keeping track of your tasks.
Pro Project support
Things 2 has a projects feature that allows you to organize your tasks together. You can select a project you need to get done and Things helps you focus on each task to get it done. You can even group projects together to focus on the most important aspect of your life at the time.

Pro Great for GTD
Things is one of the best apps of doing Getting Things Done.
Pro Nested tags
It's very easy filtering tasks that belong to various areas (etc private vs work)
Pro Responsive and easy naviagation
Logical and responsive navigation and editing. Easy to operate.
Pro Customized calendar
The calendar view (when selecting a due date for a task) is a customized, scrollable version of the default iOS calendar view. This makes it look familiar, but also functional for Things 2's requirements.
Pro Solid project management
Pro Allows setting how much effort a task will take
You can set how long a task will take and how much effort will it ask of you on a scale of 1 to 3.
Pro Allows adding items via email
Pro Use start dates
A vital functionality in a GTD app.
Pro Beautiful interface
Clean, intuitive user interaction. The design is very thoughtful. Somehow it makes Things feel clunky, despite obvious similarities of all GTD platforms.
Pro Can email focus list
The app can send you the most important items for the day in an email.
Pro Allows to add postponed tasks
You can postpone a task. It helps not to clutter task lists up until you really need them.
Pro Beautiful interface
Clean, intuitive interface — both desktop and mobile. Lots of intelligent design thinking behind this. Somehow makes other GTD apps like Things feel clunky, despite similarities.
Pro Native support for Areas of Responsibility
Cons
Con Expensive if you buy apps for Mac, iPhone and iPad (all sold separately)
As at May 2016 if buying all three apps it cost $80! That said there is no annual subscription and I've been using Things for years and have only paid once so far.
Con Poor calendar view
Could be more convenient with calendar interaction. Not an ordinary approach for visual people, if you want to see all the calendar events in the familiar format.
Con No file attachment available
Con No supported time based/location based alarms
Other apps have these abilities, and they are very useful. Especially for a $10 app, it would be great to include these premium features.
Con No way to add sub-projects
Con Does not integrate with other apps or services
Con No recur upon completion option
If you have a daily recurring task, it will recur every day regardless if it's been completed the prior day.
Con No attachments
Can't add any attachments to the tasks - no photos, no pdfs.
Con Limited features in the free version
Free version limited to 5 projects, 3 reference lists and 2 areas.
Con No desktop widget
Con No way to work with teams
This is a one-person solution, there is absolutely no ability to share projects with others.
Con No way to color-code projects
Con No bulk (copy/paste) feature
