I haven't found an open source VSCode or WebStorm addon yet that allows me to use a local model and implements code completion and commands as good as GitHub Copilot.
They either miss a chat feature and/or inline action / code completion and/or fill-in-the-middle models. And if they do, they don't provide the context as intelligently (? an assumption!) as GH's Copilot does.
One alternative I liked was Supermaven: It's really really fast and has a huge context window, so it knows almost your whole project. That was nice! But - one thing I ultimately didn't continue using it for: It doesn't support chat and/or inline commands (CTRL+I on VSCode's GH Copilot).
I feel like a really good Copilot alternative is definitely a still missing.
But: Regarding your question, I think GitHub Copilot's VSCode extension is the best - as of now. The WebStorm extension is sadly not as good, it misses the "inline command" function which IMHO is a must.
Blog post on repository context: https://tabby.tabbyml.com/blog/2023/10/16/repository-context...
(Disclaimer: I started this project)
Supermaven has a 300k token context. It doesn't seem like it has a ton of intelligence -- maybe comparable to copilot, maybe a bit less -- but it's much better at picking up data structures and code patterns from your code, and usually what I want is help autocompleting that sort of thing rather than writing an algorithm for me (which LLMs often get wrong anyway).
You can also pair it with a gpt4 / opus chat in Cursor, so you can get your slower but more intelligent chat along with the simpler but very fast, high context autocomplete.