When comparing Precursor vs Justinmind, 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 Justinmind is ranked 13th. 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.
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 Reusable components
You can create reusable components that you can use over and over again.
Pro Adaptive and responsive designs
You can create adaptive and responsive designs that will react to the viewport/screen size of the user.
Pro Functional prototypes
You can create HTML prototypes with full interactions.
Pro Supports low, med, and high fidelity
You can create simple wireframes, pixel perfect screens, or anything in between.
Pro Lots of online tutorials
The free Getting Started area has plenty of advice for getting started with Justinmind.
Pro Free forever
After one month trying the pro version, it changes to a completely free version with a few limitations.
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 Expensive
Pricing is $19 per month or $495 for a perpetual license.
Con Moderate learning curve
