VOO vs. VTI: Which Vanguard ETF Is More Likely to Make You a Millionaire?

Exchange-traded funds, or ETFs, are a great way to gain exposure to a large number of stocks in one go. Why would you want to do this rather than just invest in a few stocks? This adds diversification to your portfolio, lowering risk. For example, if a particular sector or certain stocks traverse a rough patch, others within the fund may compensate. As a result, these ETFs are unlikely to deliver extreme movements in one direction or the other over a short period of time.

And over the long term, they've often gone on to recover and gain significantly after tough times, meaning that investors who have held on for years have scored a win. So, a solid ETF could make a smart addition to your portfolio.

Two in particular, offered by Vanguard, stand out for their composition and strength over time. I'm talking about the Vanguard S&P 500 ETF (NYSEMKT: VOO) and the Vanguard Morningstar Total Stock Market ETF (NYSEMKT: VTI). Now let's consider which of these top ETFs is more likely to make you a millionaire.

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Meet the Vanguard S&P 500 ETF

The Vanguard S&P 500 ETF, as its name suggests, tracks the performance of the famous benchmark. To do this, it reflects this index's composition, so it always holds shares of the biggest companies driving the economy of the day.

This ETF includes stocks in 11 different industries, so it offers you fantastic diversification, though it's important to note that, like the index it tracks, it may be heavily weighted to favor an industry or industries that are particularly key at a given time. In recent times, this is the tech industry. These stocks make up about 37% of the ETF right now, with financials the closest follower at 12%.

So, tech stocks' performance has driven the S&P 500, and therefore this ETF, in recent years. This has been a good thing as these stocks have soared, helping the ETF gain 78% over the past three years.

Meet the Vanguard Morningstar Total Stock Market ETF

The Vanguard Morningstar Total Stock Market ETF tracks not only the large caps that are in the S&P 500 but also the stock market's mid- and small-cap stocks. It mimics the composition and therefore the performance of the Morningstar U.S. Total Market Index.

So by investing in this ETF, you'll maximize diversification by including companies of various sizes. This could be interesting as it offers you exposure to certain players early in their growth stories, so that you may benefit if they're successful and their shares explode higher.

That said, this fund's performance hasn't differed greatly from that of the Vanguard S&P 500 ETF over time, and that's due to the fact that their top 10 members are identical, including major tech names Nvidia, Apple, Microsoft, and Amazon.

And they have helped the Vanguard Morningstar Total Stock Market ETF to deliver an increase of 77% over the past three years, in line with the S&P 500 ETF.

The Verdict: Which is most likely to make you a millionaire?

First, a quick note about why these funds have achieved similar performance even though the S&P 500 ETF holds 500 stocks and the Total Stock Market ETF includes more than 3,000. The presence of giants such as Nvidia and Microsoft in the top 10, with weightings of more than 5%, has a clear impact on index direction. Many smaller companies have extremely low weightings, meaning their movements won't greatly impact the Total Stock Market ETF's performance.

The S&P 500 ETF, over time, has outperformed the Total Stock Market fund, though by a small margin. For example, over the past decade, the former climbed 256%, while the latter advanced 240%. And the S&P 500 has delivered an average annual return of 10% over the long run -- if this continues, a monthly investment of a few hundred dollars over, say, 35 years, could make you a millionaire.

These funds are very close in many ways, including performance, but the S&P 500 ETF may be a slightly better millionaire-maker due to its focus on the very strongest companies of the times.

Adria Cimino has positions in Amazon. The Motley Fool has positions in and recommends Amazon, Apple, Microsoft, Nvidia, and Vanguard S&P 500 ETF. The Motley Fool has a disclosure policy.