Most larger gangs I have seen go through different phases. They start out as small gangs with big ambitions, they try hard, and gain reputations and members. Once they establish, they can often feel they have something to prove, and go a bit wild, focussing on combat too much. This then brings criticism, and they adapt again, putting more focus on RP and player interactions. Once they hit the top 10, they often go one of 2 ways. Either they get too big for their boots, take the piss and get removed, or they settle into a comfortable medium, turning into a gang that is feared, respected, and even appreciated for their experience.
As far as who is best here, it depends on how you judge it.
I think TI are the longest lasting gang to date. I am in fact to blame for their creation. I think only 4 or 5 of their members will remember
@birchieboy (don't worry, he will never get that notification), or the brief period I came to 'co-lead' with them. Good days.
As far as RP, I think the title goes to the wonderful Marmite Miners. I remember when they first appeared I was a bit taken aback by the weird name, and unusual play style, but now I can't imagine and ALUK without them.
For me (subjective, not objective), the best gang will always be the one that took me in as Family. It was a long time ago, and very few are left, but the sense of comradery I got from playing with brothers gave me more than I could imagine. I think this is why loyal gang members will always say their gang is best. To them, it really is. Romantic maybe, but true.
