Should subheadings be placed in a seperate <h2> or should they be included with their parent <h1> heading?

For example:

Code:
<h1>Matt Sanchez</h1>
<h2>Web Designer</h2>
---------- or -------------

Code:
<h1>Matt Sanchez <span class="subHeading">Web Designer</span></h1>
Which is more semantically correct?

Thanks in advance