Both enigma.js and the .NET SDK are libraries that focus primarily on the Engine API which is based on JSON RPC over websockets, not REST. So depending on what features you are aiming at adding, you might not actually need any of them.
But to your question: Both of those libraries are fully supported, so feel free to use whatever best matches your other technology requirements. There is also a corresponding library available for Golang if that is of interest to you: