With the new Razor View Engine, should my HtmlHelpers return string or IHtmlString?

With the Razor View Engine, anytime you output a string directly to the page, it's HTML encoded. e.g.:

@"<p>Hello World</p>"

will actually get output to the page as:

<p>Hello World </p>

Which would show up in the browser as:

Hello World

Here's the problem though, when creating Html helpers, till now, with the old aspx view engine I would just return a string, and output that to the browser:

<%= Html.MyCoolHelperMethod(); %>

So my question is basically this. Do I do this:

public static IHtmlString MyCoolHelperMethod(this HtmlHelper helper)
{
   return new helper.Raw("<p>Hello World</p>");
}

in which case I can just do this in my cshtml:

@Html.MyCoolHelperMethod();

or do I do this:

public static string MyCoolHelperMethod(this HtmlHelper helper)
{
   return "<p>Hello World</p>";
}

in which case I need to do the work in my cshtml:

@Html.Raw(Html.MyCoolHelperMethod());

Obviously the first approach makes the view look a lot cleaner, but I'm just wondering if the common pattern is in fact for helpers to return an IHtmlString and I've been doing it wrong in the past.