Vanguard’s shift away from MSCI indexes has a lot of ETF investors asking key questions.

These include: Is this the right kind of move for all providers? And what does it mean for their funds’ investments?

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But shortly after Vanguard decided to ditch MSCI in favour of new benchmarks, Blackrock CEO Laurence Fink expressed his firm’s intention to stick with MSCI. The company’s been fielding calls from clients about what Vanguard’s move means for the industry, as well as about why the firm is planning to stick with the status quo.

Read: Vanguard changing target benchmarks of ETFs

And according to Greg Walker, head of iShares institutional business at BlackRock Canada, the rival firm’s announcement has opened up an important conversation about indexes and why they matter.

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“We’ve had this discussion for years about the index, and cost is only one factor. There are many more decisions investors need to make when looking at ETFs. And one of the most important is the exposure and the index itself,” he says.

The firm has issued two client memos outlining the differences between the FTSE index and the MSCI in an effort to communicate “this change is bigger than simply transitioning from one index provider to another.”

So, what’s are these differences?

When it comes to holdings, countries, sectors and styles, the FTSE and MSCI have some fundamental dissimilarities. For example, the MSCI EAFE Index and the FTSE Developed Ex North America Index have a greater than 10% difference in holdings.

Country allocations also vary between them: Korea, for instance, is a sticking point. MSCI calls it an emerging market country while FTSE classifies it as a developed country; though Korea is the second largest country allocation in the MSCI Emerging Markets Index (15.57%), it’s excluded from the FTSE Emerging Index.

FTSE’s Emerging Index also includes exposure to the United Arab Emirates and Pakistan, while MSCI’s excludes both countries, because the firm classifies them as frontier markets.

Read: Diversify emerging market exposure

So, investors need to understand that not all indexes have the same holdings, and that they’d better be primed about the specifics of the switch if they’re invested in Vanguard ETFs.

They should revisit the composition of the underlying indices they’re holding with their advisors, who also need to understand how the shift will impact their clients and their returns.

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