Hello! I am the lead developer of the Luau type checker.

I actually hadn't heard of Teal! I don't think it existed when we started.

Judging from the Teal documentation, I'd venture that it looks pretty similar to Luau in everyday use.

If I were to guess, I'd venture that the biggest differences are probably the kind of type inference we do (Luau's inference engine draws inspiration in equal parts from OCaml and TypeScript), a bunch of Roblox-specific features, and that our inference engine is all C++ for performance.