Small agile teams are the best.

When you combine agile with small projects, you get a dramatic improvement in project success rates. Small agile projects are nearly six times more likely to succeed than large waterfall projects and seven times less likely to fail.

Research by the Standish Group shows that small projects are ten times more likely to succeed than large projects and 1/2 as likely to fail, as shown below. In this research, a large project has 25 to 50 people working on it and a $6 to USD 10M budget. A small project has six or fewer people working on it and a budget of less than USD 1M.