With a large team you have more capabilities, more resources, more information and input, more ideas and possible solutions.
With a smaller team, you have more cohesion, higher member satisfaction, faster decision making/consensus, more effective individual contribution.
Bigger is the team, more innovative is the team and ease the venture and cash flow growth.
The bigger is the board of director, the better is the firm performance.
According to Jeff Bezos --Amazon CEO-- the optimal team size is the two pizzas rule team size (If a team cannot be fed with two pizzas, then it's too large.)
The optimal team size is 4 to 5 people. Jerry Useem, Fortune, 2006
4 to 5 people is best for team members satisfaction but smaller and larger team are more effective. Richard Hackman, DTIC Scientific Report, 1971
In the end, between 5-10 members on average produces optimal effectiveness... But your optimal will depend on task structure and environment.