What started as a plain-vanilla fund concept now comes in many flavors. Getty Images By John Waggoner, Contributing Writer October 3, 2019From Kiplinger’s Personal Finance Not so long ago, S&P 500 index funds came in one flavor: They simply tracked Standard & Poor’s 500-stock index. Now, the fund industry offers almost as many types of S&P 500 index funds as Baskin Robbins does ice cream. You may be best off with the plain-vanilla version, but some other variations might be worth a taste test. Prices and returns are as of September 6.SEE ALSO: 20 Dividend Stocks to Fund 20 Years of Retirement Vanguard 500 Index (symbol VFIAX), the largest and oldest S&P 500 index fund, tracks the movement of the venerable stock index and weights each holding according to its market value, which is the number of shares outstanding multiplied by the share price. Using that methodology, the fund’s top holdings are Microsoft, Apple and Amazon.com. The 10 largest stocks in the fund account for 23% of the fund’s assets. The Vanguard fund simply weights its holdings the same way the index does. It follows the index’s returns closely, and for many people it’s a fine core holding. Exchange-traded-fund fans can consider the fund’s ETF clone (VOO, $274). You can weight the S&P 500 index in different ways and get different returns as a result. Consider Invesco S&P 500 Equal Weight ETF (RSP, $108). As its name implies, this exchange-traded fund gives each stock in the index an equal weight, so that Nektar Therapeutics, with a market value of $3 billion, gets the same weight in the fund as $1.1 trillion Microsoft. The ETF is rebalanced every quarter. What’s the advantage? Invesco S&P 500 Equal Weight ETF tends to beat the market-cap-weighted S&P 500 when small-company stocks are on a tear. In 2016, for example, the equal-weight ETF beat the S&P 500 by more than two percentage points. The past decade, however, has largely seen a large-company-stock rally, and the equal-weighted choice has lagged the S&P 500 by 0.16 percentage point annualized. Advertisement Investors who foresee a comeback for small- and mid-cap stocks can consider the Reverse Cap Weighted U.S. Large Cap ETF (RVRS, $16). The smallest stocks in the S&P 500 are the largest holdings in this fund, thereby turning the large-cap S&P 500 into a mid-cap index fund. The young fund, which has $9 million in assets, lagged the S&P 500 in 2018 and trails it so far this year. The fund has held up better against mid-cap yardsticks, losing 9.4% in 2018, compared with an 11.1% loss for the S&P MidCap 400, and essentially matching the mid-cap index’s return so far in 2019. There are plenty of other ways to slice and dice the S&P 500. The ProShares Dividend Aristocrats ETF (NOBL, $71) uses only those S&P 500 companies that have raised their dividends every year for the past 25 years and weights each issue equally. The fund fares best in times when investors are worried about the stock market, because dividends can cushion downturns. The fund has lagged the S&P 500 by nearly two percentage points so far this year. SPDR S&P 500 Buyback ETF (SPYB, $66) does for buybacks what the previous ETF does for dividends. It looks for companies that have actually reduced the number of shares available over the previous 12 months. All other things being equal, a lower number of shares should give a company’s stock a boost by dividing the corporate earnings pie among a smaller number of shares. The ETF has lagged the S&P 500 over the past year, but it has kept pace with an index tracking S&P 500 companies spending the most on buybacks in relation to their market value.