I am still not sure which I need (...or both?) but either way I managed to get neither Visual Studio nor VS Code to get any code to run or compile! I downloaded and installed both SDKs but both failed to work at all - it seems there is some invisible thing configured somewhere (Windows registry? certainly not in the hello world source I was trying to write) that points to the SDK version to use, and neither the .Net nor .Net core SDKs I downloaded appeared to be the correct ones and everything chucks up error messages about the wrong SDK or missing MSBuild (whatever that is), despite just following the tutorials to do `dotnet new`. Very frustrating.
It has certainly put me off trying .net now. I wanted to migrate off of golang for my future cross-platform work, but this has really put me off - if I cant even get a hello world to work after a clean SDK install, I can only shudder to think about what the runtime dependency hell is going to be. Real shame.