Options are used for adding capabilities such as "User-Agent".

Example in C#:

var options = new PhantomJSOptions();
options.AddAdditionalCapability("phantomjs.page.settings.userAgent", 
    "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:25.0) Gecko/20100101 Firefox/25.0");

using (var driver = new PhantomJSDriver(options))
{
    //code
}

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Services are used to modify behavior of your PhantomJS instance, such as hiding the command prompt or for disabling loading images.

Here's a list of all services.

Example in C#:

var service = PhantomJSDriverService.CreateDefaultService();
service.HideCommandPromptWindow = true;
service.LoadImages = false;

using (var driver = new PhantomJSDriver(service))
{
    //code
}