When comparing Keynote vs Justinmind, the Slant community recommends Justinmind for most people. In the question“What are the best mockup and wireframing tools for websites?” Justinmind is ranked 13th while Keynote is ranked 24th. The most important reason people chose Justinmind is:
You can create reusable components that you can use over and over again.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Imports nearly every type of asset
Can import all kinds of assets (images, videos, PDFs, sounds) into mockup without hassle.
Pro Animations and transitions
Keynote currently is one of the very few tools that supports animation of elements and transition of views without programming.
Pro Text Styles makes it easy to create typography systems
Pro Smart Snaps
Keynote has alignment grids (aka snap to grid feature) that snaps to end, midpoints, baselines etc of objects and grids. They are super useful when you want to follow a structured layout for your wireframe.
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 Only available on Mac and it's file are not compatible with Microsoft Windows
Con Expensive
Pricing is $19 per month or $495 for a perpetual license.