If you've ever wanted to order everything on a menu or hit a horse-racing track looking to place a wager on all of the thoroughbreds, an index fund may be right for you. A single investment buys you a basket of stocks, and the only real research you need to dive into is deciding what basket you want to buy.

Vanguard Total Stock Market ETF (NYSEMKT:VTI) is smart choice, giving investors a way to ride the entire market at a refreshingly low expense ratio. It's also undeniably popular. Vanguard Total Stock Market ETF had $725.8 billion in assets at the end of July. Let's look at the reasons to buy the widely owned exchange-traded fund, but also size up some of the reasons some investors might want to stay away.

ETF letters on raised tiles.

Image source: Getty Images.

Reasons to buy

Vanguard Total Stock Market ETF is designed to track the CRSP US Total Market Index, a gauge that tracks nearly 100 of the country's investable equity market across all capitalizations. We're talking about nearly 3,654 different stocks, giving investors a widely diversified portfolio in the flick of a buy order execution. 

This is a market-weighted index, so it's not as if each of the 3,654 stocks takes up roughly 0.03% of the portfolio. The 10 largest holdings -- the country's 10 largest-cap stocks -- take up a hearty 18.2% of the ETF. In short, you're never entirely immune from a large-cap stock imploding.  

The Vanguard name has become synonymous with low-fee index funds, and that's just what we have here with a mere 0.04% expense ratio for Vanguard Total Stock Market ETF. It's a great way to buy into the general market without having to dedicate time to researching and tracking individual stocks, but it's not perfect. 

Reasons to stay away

If you're thinking that Vanguard Total Stock Market ETF has set the floor on general market funds, you would be wrong. Schwab U.S. Broad Market ETF (NYSEMKT:SCHB) investors shell out just 0.03% in annual expenses. That may seem like a rounding error now, but even the smallest of expense ratio differences can make a difference over time. 

The two funds aren't identical. Schwab's ETF tracks the Dow Jones U.S. Broad Stock Market Index, following just 2,427 stocks. This is 1,227 fewer names than Vanguard's entry, though at that point we're talking mostly about tiny micro caps that don't really move the needle. If you happen to have your brokerage account at Schwab, the fund also happens to be part of the 250 ETFs offered without commissions, putting more of your money to work on Schwab U.S. Broad Market ETF than Vanguard Total Stock Market ETF.

Both ETFs are solid choices, but neither one may be right for you. The two funds own only stateside companies. Vanguard Total Stock Market ETF has just 0.1% of its portfolio in foreign holdings. The concentration limits exposure to overseas markets, though naturally, many of these successful stateside business are drumming up healthy sales internationally. If you want to truly spread out your investment risk, you may want to add an international ETF to your arsenal, or find a global ETF that spans the globe. Beyond participating in the successes of overseas markets, diversifying globally also limits the sting when the U.S. market eventually corrects or retreats.

Vanguard Total Stock Market ETF is a quality investment, but it's not the only option you as an investor should be considering.