I've just been taught about a number of different design processes and philosophies, but rather than reiterate them here, I'll just give you a
link or
two.
I don't really like democracy in robotics teams because I think it's limiting to what the team can accomplish when a leader emerges and directs people's efforts efficiently. That said, I usually prefer to be the one who's leading, too, so that may give you some idea about why I feel that way.
It's a balancing act and there's no right solution. If students aren't given enough involvement or input in the design process, they may begin to resent that or feel unneeded. If a single person has the organizational skill and time available to them to oversee the entire design themselves, with criticism taken and considered, the team may build a robot that far exceeds their expectations.
At least, so I think.