Well this is of course a highly opinionated question, but I really like my own team: Quick Moves. I created it 3 months ago, and now we are in the top 350 teams on the site. All the members are nice, we have great admins, and an amazing 71% win rate on team matches. It truly is a team of friendship and unity, and because of that, I think it is the best.
Your a member of it too :P
What do you all think the best groups are for team matches and vote chess matches, or just best groups in general?