The iShares EEM ETF includes 836 holdings; Samsung Electronics, Gazprom and Chinmobile are the top three allocations; and its top ten holdings account for about 16% of the overall fund. Top country allocations include China 16.7%, South Korea 15.0%, Brazil 15.0%, Taiwan 11.1%, South Africa 7.5%, Russia 6.7%, India 6.4%, Mexico 4.6%, Malaysia 3.3% and Indonesia 2.7%.

In comparison, the Vanguard VWO ETF has 907 holdings; Samsung Electronics, Petroleo Brasileiro and Vale are the top three allocations; and its top ten securities make up 18.9% of the fund. Top country allocations include China 17.6%, Brazil 16.3%, South Korea 13.7%, Taiwan 11.2%, South Africa 7.5%, Russia 7.4%, India 7.2%, Mexico 4.6%, Malaysia 3.0% and Indonesia 2.3%.

The differences between company, country or sector weightings don’t make one ETF better than another. It is a question of what works better within your overall portfolio and what you are more comfortable with. Potential investors should take the time to examine holdings, stricture and goals of any ETF investment for the time frame you have in mind.

For more stories in the series, visit our “What is an ETF?” category.

Max Chen contributed to this article.