When comparing BYOND vs uScript + Unity3D, the Slant community recommends BYOND for most people. In the question“What are the best 2D game engines?” BYOND is ranked 29th while uScript + Unity3D is ranked 97th. The most important reason people chose BYOND is:
BYOND is in active development and updates are released constantly.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro In active development
BYOND is in active development and updates are released constantly.
Pro Easy to use
The software itself is very easy to learn and use for beginners.
Pro Helpful community
BYOND's community is relatively large and extremely helpful. Any question a beginner or an experienced user may have is quickly answered.
Pro Large Community
Fairly large player base and multiple games to play.

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 Highly supports multiplayer, but can make solo games ready for download.
Con Exclusive programming language
The language is known as DM, and is modified using Dream Maker. It is an object oriented, interpreted language, which closely resembles C++, Java and PHP. More information available in the DM Guide.

Con Not that easy to use
It's a lot more complicated compared to something like Playmaker. Same tasks take a lot more time.
