Should you invest in the American card processing giant or the American-Swiss insurer?Many investors follow Berkshire Hathaway's (BRK.A 0.87%) (BRK.B 0.96%) portfolio of nearly 50 stocks and exchange-traded funds for fresh investment ideas. It's a great starting point because those investments were hand-picked by Warren Buffett, one of the world's most acclaimed investors, and his experienced management team.That's why it was alarming when Berkshire started selling a lot of stocks -- including half of its s ...