If you mean a comparison between SPECS' paradigm, ECS, and Unity's mix of OOP/composition, the main benefit of ECS is performance. The way ECS loops over arrays

If you mean a comparison between SPECS' paradigm, ECS, and Unity's mix of OOP/composition, the main benefit of ECS is performance. The way ECS loops over arrays of data means that the memory accesses it makes are nearly always already in cache. Games spend a surprisingly large amount of time just waiting to receive values from memory. In the right circumstances, normally when dealing with huge numbers of objects (think simulation games), ECS can be entire orders of magnitude faster. Other than that some people just prefer coding in ECS. Unity has been developing its own separate ECS framework for a while now.