I have an Arduino board in a location, and a webserver.
I also have a website that is supposed to control the Arduino. What technique would allow users to take control of the Arduino board with the least amount of latency?
You should have a look at Socket.IO for implementing WebSockets on server- and client-side.
There's a great project called duino for accessing Arduino with Node.js, you "only" have to pipe all communication through WebSockets.