While it is hard to knock the advice of Warren Buffett, whose annual letter to Berkshire Hathaway Inc shareholders recently lofted down from the mountain of capitalism, some of his tips can be tweaked.

Among the many nuggets of wisdom in the Berkshire report was a recommendation from the company's chairman to the trustee of his estate that 10 percent of the cash be invested in short-term government bonds and 90 percent in a "very low-cost index fund (Vanguard's)."

Buffett is spot on about holding onto an index fund and avoiding the exorbitant fees of active managers. But we should look at his advice a bit more closely.

In an earlier Buffett blog on Fortune.com, the legendary investor cited the ticker symbol for the Vanguard 500 Index fund (VFINX). The fund charges 0.17 percent in annual expenses and owns the top 500 U.S. stocks by market capitalization, such as Apple Inc., Exxon Mobil Corp. and Google Inc. As of Friday, it was up about 2 percent year to date.

In line with Buffett's penchant for penny-pinching and focus on long-term returns, I was wondering if you can find a better index fund. You can certainly find a cheaper fund that tracks the Standard & Poor's 500 stock index.

Vanguard's exchange-traded S&P 500 Index fund charges only 0.05 percent annually and trades commission-free through many discount brokers, including Vanguard.

I would also call into question Buffett's selection of the Vanguard 500, which picks a near-static basket of the most popular U.S. stocks, many of which could be overvalued.

What might appeal more to Buffet's bargain-picking acumen would be a fundamental S&P 500 fund like the Guggenheim S&P 500 Equal Weight ETF (RSP), which owns roughly equal percentages of stocks in the index, including lesser-known companies like LSI Corp., Harman International Industries and F5 Networks Inc.

Instead of overweighting the most popular stocks the way most S&P 500 funds do, the Guggenheim fund tilts in the favor of lower-priced companies that pay regular dividends. This strategy beat the S&P 500 index for the past decade by almost two percentage points. It is up 3 percent year to date, compared with about 2 percent for the S&P 500, and costs 0.40 percent annually to own.

Even though Buffett is recommending them, far too many investors may think index funds are too staid for their tastes. They will want to achieve stellar returns like Buffett has over the past 50 years. Although it is hard to quibble with Buffett's compounded performance at Berkshire Hathaway - the overall gain is 693,518 percent from 1964-2013 - the big jumps came quite a while ago.