When comparing Producteev vs GTDNext, the Slant community recommends GTDNext for most people. In the question“What are the best cross-platform task apps?” GTDNext is ranked 13th while Producteev is ranked 46th. The most important reason people chose GTDNext is:
All the “Get Things Done” lists you would expect: next actions, someday, waiting, and scheduled.
Specs
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Pros
Pro Separate networks and projects
This helps separate personal tasks from work tasks and makes it easy to differentiate between projects/contexts.
Pro Free plan is feature-rich
The free version includes lots of features other services charge for (attached files and more).
Pro Multiple reminders per task
You can set a single task to have more than one reminder.
Pro Simple access to almost any desired feature
It doesn’t take many clicks to access all of the features.
Pro Designed to work in team
Tasks can be assigned to specific individuals, or you can add followers. All people involved will receive notifications. The project can be shared with the full company or within selected subgroups.
Pro Real-time and custom push reminders
Some apps (Basecamp, Asana) don't have this.
Pro Apps for every platform
There are dedicated apps for almost every platform.

Pro GTD style lists
All the “Get Things Done” lists you would expect: next actions, someday, waiting, and scheduled.

Pro Automatic next actions
When it comes to choosing your next action, most to-do apps suffer from the same problem: All of your actions (sometimes hundreds in total) are visible to choose from. This can overwhelm users and cause them to give up on the system. GTDNext is different. In the "Next Action" view, only the very next action is shown for each of your projects. This results in a nicely consolidated view of only the things that need your immediate attention.

Pro Unlimited levels of projects and actions
In GTDNext you can set up an unlimited number of levels for your projects and actions, allowing you to plan your project and sub-projects in as much detail as needed.

Pro Areas of Focus
GTDNext supports the “Areas of Focus” methodology from Getting Things Done. You can filter all of your tasks to just show your work tasks, side project tasks, or personal tasks. There is also a global filter, so that when you’re hard at work you can focus only on your work projects and tasks.
Pro Option to visualize all projects and tasks in a single outline view
This is really useful because it prevents you from having to navigate through each project individually.

Pro Many keyboard shortcuts available
The number of keyboard shortcuts makes it easy to log or add tasks without removing your hands from the keys.
Cons
Con No mobile app available
Con Web only
GTDNext does not have native apps for other devices, but it does work across PC/Mac/Linux on the web client.
Con No Google Tasks integration
