In well-functioning families, decision making is task centered. Usually, anyone needing a decision either has or can earn the right to make the decision. For example, your ten-year-old may be told when to study. By twelve, she may get a little encouragement. By fifteen, studying is her task and when to study is her decision. Even then, though, she probably will not be the one to decide whether she studies; she just decides when. At the same time, she may be the one to decide about her bed time but not about whether she gets up to go to school. You still decide that she has to go to school.
Somewhat less functional is decision making that is participatory. This is hard to see since it is a method often presented as the best way. The idea is for all family members to participate in most decisions. The implication is that participation is like having a vote.
When stated this way, the risk is easier to see. Not everyone does or should have a vote. Getting the ideas and opinions of others and taking them into consideration is different than everyone having a vote.
"I will think with you about the problem; but I will not decide for you. It is your problem and your decision. You and I will talk about the problem and then you will decide."
The participatory approach would be, "You and I will talk and then we will decide."
Autocratic decision making is more obviously risky. The autocrat (usually an adult but sometimes a child) makes all decisions based on whatever pleases or seems best to him/her. No one else makes decisions or learns how to make decisions, for that matter.
At the extreme, decision making is paralyzed. No one decides and nothing gets resolved. An autocrat can at least decide something. This says nothing about the quality of decisions; but even bad decisions may, in the long run, be better than no decisions.