mozilla extensions

[Dimitris Tsamis]

I use Firefox and Thunderbird on FreeBSD and I have noticed that some of
the extensions are available as ports, for example the adblock and
enigmail extensions. I want to ask if there is a difference between
installing the port and installing the extension from an xpi file.
Especially for Thunderbird I see that the version available for FreeBSD
on the official enigmail site is 0.89.6, whereas the port installs
version 0.93.0. Why is that?