Different ways to write memcached

I'm checking my server config while looking on internet for some tips and I have noticed that memcached is writtent in different ways.

I'm referring to this part of app/etc/local.xml:

<cache>
    <backend>memcached</backend>
...

In particular I have seen these ways:

• memcache inside local.xml.additional and some tutorials


• memcached on hosting sites and tutorials


• Memcached inside one or two tutorial and stackoverflow answer

My question is: is there any differents? if yes which one is correct?