Again scale matters. The SMI, leading Swiss stock market index is comprised of 20 components which represent 80% of the total capitalization. Compared that to S&P 500's components representing similar total cap.
When you look to aggressively grow your portfolio you are not looking at economies that scale. You look for companies that aggressively grow, offer superior product at competitive pricing, and where barriers of entry are high. That can be in developing markets equally as in saturated economies. Almost always the highest growth is observed in midsized companies, you don't need to go with large caps. The work lies in combing through the many companies that potentially qualify.