In general? I've found, with my kids, that it helps immensely (in the general character-building sense) for them to do something they're not particularly good (read: pretty lousy) at. They get a healthy dose of being just one of the crowd (which is a lot easier at six than sixteen or twenty), plus they have the opportunity for feeling a real sense of achievement by working hard to become halfway decent at it. If it involves being part of a team, so much the better, because there are about a thousand other associated (lessons to be gained along the way.)
I'm not sure about that. I had sports inflicted on me early in life and the only thing that ended up giving to me was an enduring hatred to sports, particularly team sports. I never really got better.
The only thing that being part of a sports team taught me was that I was an unnecessary liability and of no value to the team. Also, that I really hated being part of teams.