understanding key usage

Hi,

is there a difference between the following?

<xsl:key name="dkey" match="B" use="key"/>
  <xsl:for-each select="value/B[generate-id()=
generate-id(key('dkey','USD')[1])]">

and

<xsl:for-each select="value/dovizler[key='USD']">

in my opinion, both of these correspod to B elements whose 'key' values are
equal to 'USD'.

any ideas?
regards.