Actually, there are four forms of this operator:
<>
!=
^=
and even
¬= -- worked on some obscure platforms in the dark ages
which are the same, but treated differently when a verbatim match is required (stored outlines or cached queries).
According to this article, != performs faster
At university we were taught 'best practice' was to use != when working for employers, though all the operators above have the same functionality.
Source: Stackoverflow.com