Knockout, league or groups: which should I pick for my competition?

• Knockout. Lose and you're out. Quick, and it builds to a final. The usual pick for a one-day competition.
• League. Everyone plays everyone, once or twice. Everyone gets the same number of games, so it takes longer.
• Groups, then a knockout. Players are split into small groups, and the best from each go into a knockout. Everyone gets a few games before anyone goes out.

You can also have a knockout where players are paired up again at the start of every round, so nobody knows who they're playing next. In the competition's settings, under Draw type (the draw is who plays who), pick Live draw.