Ranked in these QuestionsQuestion Ranking
Pro Easy to embed in C or C++ programs.
Mruby is far more easy to embed in C or C++ programs than other scripting languages. No need to manage the stack, you just get the arguments back in your wrapper function and convert them from mruby to C with a single function call.
Pro A powerful, flexible OOP scripting language.
Mruby implements most of Ruby up to the 1.9 version. This means you get an extremely powerful scripting language with many features such as true OOP, lambdas and blocks, garbage collection, lexical scoping, mixins, built in arrays and hash maps, powerful string manipulation functions, ...
Pro Rather lightweight
Of all the Ruby implementations, mruby is the lightest and easiest to embed into your C or C++ game.
Con Smaller ecosystem than plain Ruby
Mruby is less popular than plain Ruby, and newer. It is less well documented.
Con Using the garbage collector needs some thought
The mruby garbage collector is more eager than that of Matz Ruby. It is sometimes neccesary to call mruby write barrier functions to protect allocated mruby memory from collection.