What is the difference between jedi and python language server in VS code IDE?
Jedi is an auto-completion library written in Python while the language server is implemented in C#. The latter was done for performance and to share a common code base between the Python extension for VS Code and the Python workload of Visual Studio. Eventually the language server will become the default experience in the Python extension for VS Code.
As for the memory issues, they are being actively worked on, so do make sure you are trying a new version of the language server (0.2.65 is the latest as of this writing). And if you are still having memory issues please file issues as appropriate.