When comparing Prototyping on Paper vs Keynote, the Slant community recommends Keynote for most people. In the question“What are the best tools for prototyping mobile interactions/animations?” Keynote is ranked 7th while Prototyping on Paper is ranked 20th. The most important reason people chose Keynote is:
Can import all kinds of assets (images, videos, PDFs, sounds) into mockup without hassle.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Multiple device support
Prototyping on Paper supports both Android and iOS.
Pro Based on sketched wireframes
Prototypes made on PoP are based on sketches made on paper or a whiteboard, which are later photographed or scanned and uploaded into the app. Once that's done, hotspots can then be added, which register tapping or several gestures.
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.
Cons
Con Not well suited for complex prototypes
PoP is built to be a tool for quick prototyping, especially in participatory design sessions. For complex prototypes with a lot of screens it would require a large number of images to be used and this can make any project hard to maintain.