On grouping in XSLT and EXSLT

Everybody knows grouping in XSLT is kinda advanced topic. Muenchian method is just a nightmare for XSLT newbies and XSLT-related newsgroups are full of help-me-to-group-in-xsl postings. Well, and I and fellows do answer such questions day afer day. Should admit that's a way booooring. Now I wonder why we don't use EXSLT to simplify grouping technique so even newsbies can grasp it quickly? I'm talking about set:distinct function, which can replace the dreadful and mysterious generate-id()=generate-id(key('theKey', foo)[1]) step in Muenchian method.

Here is a common grouping sample along with both classical solution (pure Muenchian method) and improved one (EXSLT-based). So compare and say which is more understandable.

Source XML, list of cities.

<doc>
    <city name="Paris" country="France"/>
    <city name="Madrid" country="Spain"/>
    <city name="Vienna" country="Austria"/>
    <city name="Barcelona" country="Spain"/>
    <city name="Salzburg" country="Austria"/>
    <city name="Bonn" country="Germany"/>
    <city name="Lyon" country="France"/>
    <city name="Hannover" country="Germany"/>
    <city name="Calais" country="France"/>
    <city name="Berlin" country="Germany"/>
</doc>

<doc>
    <country name="France">
        <city>Paris</city>
        <city>Lyon</city>
        <city>Calais</city>
    </country>
    <country name="Spain">
        <city>Madrid</city>
        <city>Barcelona</city>
    </country>
    <country name="Austria">
        <city>Vienna</city>
        <city>Salzburg</city>
    </country>
    <country name="Germany">
        <city>Bonn</city>
        <city>Hannover</city>
        <city>Berlin</city>
    </country>
</doc>

Solution #1, classical Muenchian method:

<xsl:stylesheet version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:key name="kCountry" match="city" use="@country"/>
    <xsl:template match="doc">
        <doc>
            <xsl:for-each 
select="city[generate-id()=generate-id(key('kCountry', @country)[1])]">
                <country name="{@country}">
                    <xsl:apply-templates select="key('kCountry', @country)"/>
                </country>
            </xsl:for-each>
        </doc>
    </xsl:template>
    <xsl:template match="city">
        <city><xsl:value-of select="@name"/></city>
    </xsl:template>
</xsl:stylesheet>

Solution #2, EXSLT based one:

<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
xmlns:set="http://exslt.org/sets" exclude-result-prefixes="set">
    <xsl:key name="kCountry" match="city" use="@country"/>
    <xsl:template match="doc">
        <doc>
            <xsl:for-each select="set:distinct(city/@country)">
                <country name="{.}">
                    <xsl:apply-templates select="key('kCountry', .)"/>
                </country>
            </xsl:for-each>
        </doc>
    </xsl:template>
    <xsl:template match="city">
        <city><xsl:value-of select="@name"/></city>
    </xsl:template>
</xsl:stylesheet>

Both stylesheets are almost the same except bolded parts. My measurements (using nxslt.exe with -t option) say it takes the same time to execute both stylesheets and frankly I don't see why it could be different. But set:distinct(city/@country) and city[generate-id()=generate-id(key('kCountry', @country)[1])] do differ, don't they?
Well, the only obvious contra is that Muenchian method is portable as pure XSLT, while EXSLT based method relies on optional EXSLT implementation.