When comparing Precursor vs Axure, the Slant community recommends Precursor for most people. In the question“What are the best mockup and wireframing tools for websites?” Precursor is ranked 9th while Axure is ranked 15th. The most important reason people chose Precursor is:
A free tier with all mockup functionality is available. Free tier is limited by lacking ability to save mockups privately and additional services provided by Precursor like voice chat and registered subdomains.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free tier
A free tier with all mockup functionality is available. Free tier is limited by lacking ability to save mockups privately and additional services provided by Precursor like voice chat and registered subdomains.
Pro Collaborate in real time
Share a link with teammates and they can jump right into your doc. You'll see their changes as they happen, and the built-in voice chat makes design meetings effortless.
Pro Highly polished UX
Pro Supports web and mobile prototyping
Allows creation of interactive HTML mock-ups which is accessible for both websites and mobile applications.
Pro Lots of options for sharing your work
Great web options, but you can also save your wire frames out to Word and convert the notes to annotations.
Pro Resuable components
You can create a component (widget) that you can use over and over again.
Pro Cross-platform
Available for use on Windows and Mac.
Pro Collaboration tools
You can set up a project with SVN-like check-in/out system to work with others.
Pro Offers resources to help you get proficient with the software
There is a wealth of online training including videos for getting the basics down, a great community to mine, and support team to help assist with more technical details.
Cons

Con Really simplistic
Basic tools (line, square, circle) wich do no stick together: if you move a circle the attached line won't move making reengineering the model simply impossible
Con Moderate learning curve
Con Expensive [$289-$589]
There is a free trial to work with Axure, but there is a hefty price for the standard edition at $289. Even more so, the Pro edition will cost $589.
