It's a new month and a new opportunity to invest. When it comes to investing ideas, I can't think of a better fount of wisdom than Warren Buffett. His Berkshire Hathaway (BRK.A -0.29%) (BRK.B -0.17%) portfolio features plenty of great stocks.

But if I could buy only one Buffett stock in May, which one would it be? It's both a difficult and an easy decision.

Eliminating a few top contenders

Buffett's biggest position in Berkshire's portfolio by far is also my personal biggest individual stock holding -- Apple (AAPL 0.37%). Like Buffett, I think that Apple has great long-term prospects. Where I differ from the Oracle of Omaha, though, is in the importance of not having too many eggs in one basket. As much as I like Apple, I already own too big of a stake to feel comfortable buying even more shares right now.

My view is that Buffett's second-largest holding, Bank of America (BAC 1.34%), looks attractively valued after sinking by a double-digit percentage so far this year. The main problem with buying BofA, however, is that the dust hasn't yet settled with the turmoil that has rattled bank stocks in recent months. I expect Bank of America to rebound strongly, but it could take a while.

I also rank Amazon (AMZN 0.59%) as one of the best stocks to buy and hold over the long run. In particular, my prediction is that the company's Amazon Web Services (AWS) unit still has massive growth potential with the transition of apps and data to the cloud. But Amazon isn't my top Buffett stock to buy in May for reasons I'll soon explain.

Potential recession picks

The Federal Reserve seems to think that the U.S. economy will likely enter a recession this year. Many economists agree. So do I. With this in mind, I think that a few Buffett stocks should hold up relatively well.

Two of them are healthcare stocks -- Johnson & Johnson (JNJ 0.31%) and McKesson (MCK 0.77%). J&J could have an edge because it's been a longtime go-to pick for investors during times of uncertainty.

The other three are in the consumer defensive sector. The Coca-Cola Company (KO -0.46%), Buffett's longest-held stock, shouldn't miss a beat if a recession comes. Grocery giant Kroger (KR -1.25%) seems likely to perform better than most stocks in an economic downturn. Procter & Gamble (PG 0.32%) would probably be in the same boat with consumers buying its products no matter what macroeconomic conditions are.

I suspect that any of these five stocks would be great picks if a recession is right around the corner. However, none of them is my top Buffett stock to buy this month.

My top Buffett stock for May

Don't worry -- I won't try to build the suspense further. If I could buy only one Buffett stock in May, it would be... Berkshire Hathaway.

My rationale is simple. Investing in Berkshire allows me to scoop up shares of great long-term picks such as Apple, Bank of America, and Amazon. Buying the stock also gives me several solid recession plays, including Johnson & Johnson, McKesson, Coca-Cola, Kroger, and Procter & Gamble. In addition, I get dozens of other stocks plus ownership in Berkshire's own strong insurance, energy, and other businesses.

Buying Berkshire Hathaway shares also puts two of the world's greatest investors -- Buffett and his longtime business partner Charlie Munger -- to work for me. I sort of look forward to seeing what they might do with Berkshire's massive cash stockpile if a recession pulls stock valuations down significantly.

Will Berkshire perform as well over the long run as Apple or Amazon? Will it hold up as well during a recession as Coca-Cola or Johnson & Johnson? The answer is probably no on both questions. However, Berkshire provides a significant level of diversification with exposure to all of these stocks and more. I suspect if Buffett could buy only one stock in May, he'd pick Berkshire too.