The big difference between IPB and phpBB is the price. One is free and the other is not.
Any feature that you can find in IPB, can be found in phpBB. phpBB is just the starting point ... a basic package that can be added to very easily with a whole slew of mods and add-ons. They even have a module called EZY-Mod which will do the mods automatically.
There are portal solutions for phpBB. Two portal mods can be found at the phpBB main site. In fact the main phpBB site is a portal of sorts, and it is a good example of what you can accomplish with it. If you do not want to go thru the trouble of fiddling with the code, there is a complete phpBB Portal package called Minerva which is also available for free at
http://www.flexion.org
phpBB has a true templating system and anyone with basic Html experience can create their own themes (skins). In fact there are probably more of these in the phpBB world than IPB's.
As for speed ... any of the packages can be improved upon. If you want to see fast ...
this is fast. Just like IPB, phpBB supports GZIP compression also. Plus it has page caching to reduce Server load.
Installation ease ... no difference. Support ... tons of it on the main site plus there are a number of phpBB author sites (it is a community of them) with even more support. One in particular would be Craven de Kere's
http://www.Able2Know.com site ... he is the one with the
SEO mod that is very popular.
Now the big news. phpBB version 2.1.x is available for testing (not for live production!!!). This the development version for 2.2.x and they are currently at the half-way mark. phpBB 2.2.x is going to rock, and blow away the previous version of 2.0.x and any other Forum software out there (hands down and a fact)
If you want to test drive phpBB (including the Admin side of things) visit
OpenSourceCMS phpBB 2.08a Demo. OpenSourceCMS also has some other forum software to try out also -- openBB, Phorum, W-Agora, and XMB (I am not familular with these though).
Some phpBB Related site of value are:
phpBB Hacks - Largest collection of mods for phpBB.
Niels Mod Site - This is the number one phpBB mod author site. He is responsible for the EZmod module that will be incorporated (to some extent) into the new release of phpBB. This site is very busy with over 12,000 ACTIVE users (the site is set to delete your account after 30 days of inactivity).
Smartor Site - Smartor is behind a lot of the Portal solutions for phpBB ... plus some other foo-foo stuff too.
phpBB.de - The European extension of the main phpBB site. Don't worry ... it is in English. (good example of the Language support they have for phpBB). This is also another example of the Minerva Portal solution applied to it.
Styles Demo Board - Name says it all.
Another Style Demo Board
Jasidog Themes - This guy is PhotoShop on steroids ... a little too rich for me, but just another example of what the phpBB community is capable of (He does IPB skins also Matauri ;-)
phpBB 2.2 Development FAQ - 2.2
Feature List [ updated 25 May ] -
phpBB 2.2 M-2 completion ... and M-3
Finally, if you cannot find it there ... I will be more than happy to help out. I have a
Test Site (before going to live production) that you can get some extra help. It is a closed site, so let me know if you are coming.