Visual Studio uses the same compiler written in TypeScript/JavaScript. The Visual Studio integration is done in C# but only for interop with the Visual Studio APIs, there is only one version of the TypeScript compiler.
I know when Palantir was developing Eclipse tools for TypeScript they posted to the Codeplex project regarding performance issues and the team from MS responded with suggestions about caching and only recompiling the minimal targets necessary.
This. at least the js one. Maybe VS is bundled with a Typescript compiler written in C# , i dont know,but clearly the javascript one is damn slow.