OpenWebKitSharp gives you full control over WebKit Nightly, which is very close to webkit in terms of performance and compatibility. Chrome uses WebKit Chromium engine, while WebKit.NET uses Cairo and OpenWebKitSharp Nightly. Chromium should be the best of these builds, while at 2nd place should come Nightly and that's why I suggest OpenWebKitSharp.
http://gt-web-software.webs.com/libraries.htm at the OpenWebKitSharp section