“If” Example Questions

Consider this fragment:

<r:recipe>
  <dc:title>Recipe Title</dc:title>
  <r:name>Recipe Name</r:name>...
</r:recipe>

How are these three different?

<xsl:variable name="title" select="(r:name|dc:title)[1]"/>

<xsl:variable name="title">
  <xsl:choose>
    <xsl:when test="r:name"><xsl:copy-of select="r:name"/></xsl:when>
    <xsl:otherwise><xsl:copy-of select="dc:title"/></xsl:otherwise>
  </xsl:choose>
</xsl:variable>

<xsl:variable name="title"
              select="if (r:name) then r:name else dc:title"/>