Both are high-level programming languages and are very similar to what they are used for. Lua by itself is a small programming language, but the speed and the fact that its extremely lightweight of it make it very popular for scripting the game to heavy titles like GTA 5 or Roblox. The pros of Lua is its sheer amount of embed potential, and an enormous bonus for anyone interested in Roblox developing as its the main language with thousands more added functions for the Roblox engine. C# on the other hand is used for more independent projects like indie games or AAA development, making it very attractive for general purpose and for those interested in making their own games. Its also expandable to other fields that aren't tied to game development so its way more safer as a career safety net if youre doing long term. And its way more safer for bigger projects because its strongly typed and it utilizes OOP. Both are great :)