This caught my attention in a thread at ns.org:

Originally Posted by Redford

saying that the only diffrence between pubbers and clanners is skill is absurd. There is also a very definite mental diffrence between the two.

Pubbers enjoy casual play. They have fun with the mod either by just screwing around, or enjoying games with friends or complete strangers. They don't care if they win in most cases as long as they have fun getting there. Casual gamers want rules that make the game fair, and will increase the fun-factor of the game without introducing exploitable or frustrating elements. They often react violently towards playing with clanners because clanners often use tactics which are considered "unfair" or "lame" by them.

Clanners on the other hand, enjoy professional play. They play to win at all costs - nothing else is important. They will do anything to prove themselves superior to their opponenet, which often leaks down into other forums of communication. This creates the well known "Clanner attitude". Clanners will do anything to win. They enjoy playing with people who share their same attitude and are therefore not fodder for the previous points. They want a mod that is balanced only at the highest level of play (which they play on) and do not care if it has rammifications further down the ladder. They also want elements included that can be practiced using skill in order to get better, even if those elements are nearly (or are) engine, game, or bug exploits.

These are only general demographics for the two mindsets. Please don't reply saying OMG THIS ISNT HOW I AM?!?1/1/ becuase these are the most severe representations. Some people are midway between the two mindsets, grabbing behaviors from both. Some clanners (a very small item) enjoy playing compeditivly yet also understand respecting others and the merits of casual play - these are the best of both worlds, and mostly the element that was allowed to remain in the PT program after the vets were split.