When comparing SpriteKit vs uScript + Unity3D, the Slant community recommends SpriteKit for most people. In the question“What are the best 2D game engines?” SpriteKit is ranked 54th while uScript + Unity3D is ranked 97th. The most important reason people chose SpriteKit is:
Easy to access in Xcode.
Specs
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Pros
Pro Built-in in Xcode
Easy to access in Xcode.
Pro Awesome performance
One of the most efficient frameworks. If you need to build an iOS game, this is the best solutions.
Pro Automatically generates nodes for third-party script assets
uScript's nodes are a visual representation of actual code blocks, and it takes advantage of C#'s reflection capabilities to automatically create nodes for any scripts it finds in your project, regardless of the source. This makes it inherently compatible with pretty much everything.
Custom nodes can also be created by hand, for cases where the automatically created ones contain more elements than they actually need.
Pro Versatile flow diagram script model
Modeled after UDK's Kismet (the predecessor to UE4's Blueprint), uScript's scripts resemble flowcharts where each box represents a function or value, with connections between them representing program flow. This provides a better at-a-glance indication of game logic than a simple list of events, and makes complex behaviors easier to accomplish.
Pro Generates C# source code
Nodes are translated directly to C# files in your project. This is great for learning to code, and also for advanced users who can use uScript for fast prototyping and then further optimize the scripts if necessary.
Cons
Con Restricted in apple ecosystem
This is an Apple technology and its use is restricted to iOS and OSX systems.
Con Not that easy to use
It's a lot more complicated compared to something like Playmaker. Same tasks take a lot more time.