It’s possible to use the Visual Studio diff tool to compare any two files.
In the Command Window type in Tools.DiffFiles followed by the two filenames. You will see there is even an auto-completion feature.
While external diff tools can be better than Visual Studio’s built-in, it has the advantage of being available everywhere you have a Visual Studio install (like on a client’s machine where you can’t install software, or a co-worker’s machine when you are giving him a helping hand).
It’s a very solid diff tool and Visual Studio users are already familiar with it from using it for merges.