With a vast array of choices in every investment sector, ETF investors have their work cut out for them. But picking the best fund from among several with similar strategies or names can be painless if you bear these points in mind:

• How similar are they really? Not all ETFs tracking the same market segment are created equal. Similar-sounding ETFs may vary widely in terms of their holdings if their underlying indexes give different weightings to stocks. For example, SPDR S&P 500 (ARCA:SPY ) is weighted by market capitalization, which means larger companies hold a bigger slice of the total asset pie.

But some investors may be willing to take on added risk for the chance of greater returns. So they might consider Guggenheim S&P 500 Equal Weight ETF (ARCA:RSP ), which gives all companies the same billing regardless of asset size.

There is no perfect fit for every investor; rather you must select holdings that conform to your risk tolerance and investment objectives, said David Fabian, managing partner of FMD Capital Management in Irvine, Calif.

• What is in the funds? Even novice investors usually know to examine the fund’s performance and market exposure, but often fail to consider one key element, said Philip Blancato, chief executive of Ladenburg Thalmann Asset Management in Manhattan: What are you actually buying in an ETF? Investors should be mindful of the methodology because despite the names or investment objectives of two ETFs being similar, their country, region and sector exposure could be significantly different.

Take iShares MSCI Frontier 100 (ARCA:FM ) and Global X Next Emerging & Frontier ETF (ARCA:EMFM ): While FM offers almost 100% exposure to frontier markets and 22% to Kuwait, EMFM’s corresponding exposures are 27% and 1.9%. So as an ETF investor, you’ve got to study the index, Blancato said. Is the index reflective of what you want to buy?

• How do the costs compare? Not all sector funds guarantee investors the low fees that ETFs are justly famous for. Expect actively managed and tactically oriented ETFs, which often use a more sophisticated stock-picking method, to cost more than a passive, index-based fund.

Indeed, First Trust Dow Jones Internet Index Fund (ARCA:FDN ) has an expense ratio of 0.60% more than three times that of $13 billion Technology Select Sector SPDR ‘s (ARCA:XLK ) 0.16%. FDN selects Internet commerce and service companies using measures such as average share volume, whereas XLK gives investors broad exposure to the technology sector.

When comparing products, make sure you analyze (fees) to determine the best option that fits your needs, said Fabian.

• Are they equally good? Finally, it is worth comparing a few other traits: the ETFs’ asset size, new investments, number of shares traded daily and performance vs. the index they track.

According to Blancato, investors should first focus on the ETF’s liquidity. A relatively illiquid product trades less than 100,000 shares a day. Retail investors may assume that this is irrelevant to them because they are only buying 100 or 200 shares, he noted.

But relevancy comes if you need to exit the security in a downward market: You’re going to have extreme pressure on price which you would not expect, and that’s your first and foremost risk, he said.