Jalokim wrote:here is a brief look at all the versions and my recommendations.

phpbb2 :
This is the first phpbb version on forumotion, it also has a very high
popularity rate, but that is only because of its time on the internet.
For me phpbb2 is very basic, it has a simple layout, little
customisation capabilities. That is why forumotion added template
editing to phpbb2. This paid service gives you the ability to add
custom blocks and entirely change the view of your forum... you can add
new items, but i still think the general style is not to fancy.

it is the most stable, forum version.

phpbb3:
This is phpbb2's successor. it is a newer, faster, sleeker version of
phpbb2. It offers a whole load more customisation , and looks very
modern. It is web 2,0 based.
It doesn't have template editing, but the CSS lets you customise your forum.

punBB:
This is stand alone forum version. It is very easy to use and elegant.
If you are looking at a high class forum experience and ease this is
the forum type. It looks different from the phpbb versions. The CSS
allows for very flexible modifications of the forums looks.

invision/IPB:
This is my favorite. it is one of the most modern systems. It has an
advanced CSS and allows you to customize your forums looks without
limitation. This is internet user based. Its for members that know how
forums function and want to pull the most out of their forum experience.


All the versions are very similar, they are all really stable and offer almost identical mods and services.
my recommendation is IPB, especially if you into customization.
punBB for ease of use
phpbb3 for modern and sleek
and
phpbb2 for a more ... eh ancient approach to foruming, may I remind you
that phpbb2 is scheduled to be removed in a while (within 2 -3 years)