If your top priority is fast inline autocomplete across a polyglot IDE workflow, the usual top picks are:

Best overall for speed + inline autocomplete

GitHub Copilot

• Very strong inline completions
• Broad language support
• Best “it just works” experience in VS Code, JetBrains, Visual Studio, Neovim, etc.
• Usually the safest default if you want low-friction autocomplete in many languages

Best if you want a more “autocomplete-first” feel

Codeium

• Often feels very quick and lightweight
• Good multi-language support
• Strong value if you want aggressive inline suggestions without paying much
• Popular for teams that want broad IDE support and fast completions

Best for privacy/self-hosting concerns

Tabnine

• More enterprise/privacy-oriented
• Works across many IDEs and languages
• Good if code locality and policy controls matter more than absolute suggestion quality

Best if you want strong chat + coding help, not just autocomplete

Cursor or GitHub Copilot Chat

• Great for agentic workflows and code editing
• But if you specifically mean fast inline autocomplete, Copilot/Codeium are usually better-known for that single job

Quick recommendation

• Best default: GitHub Copilot
• Best lightweight/cheap alternative: Codeium
• Best enterprise/privacy: Tabnine

What matters most for this use case

For inline autocomplete in a polyglot IDE, the deciding factors are usually:

1. Latency — how quickly suggestions appear
2. Suggestion quality — especially across languages/frameworks
3. IDE coverage — VS Code, JetBrains, Vim/Neovim, etc.
4. Acceptance behavior — whether completions are unobtrusive and accurate
5. Privacy/policy — especially for company codebases

If you want, I can also give you a ranked comparison table by IDE (VS Code, JetBrains, Neovim) and language stack.