Two years ago I owned Amgen when they were being relentlessly hammered, due to issues with their anemia drugs. Back then Amgen's stock price was in the 40's, while Gilead Science's stock price was in the 50's. Nearly everyone I told about the position told me that Gilead Sciences was growing much quicker and was the better investment. Sell side analysts agreed.
Gilead did indeed grow much quicker but the valuations changed as Gilead used to trade for more than twenty times earnings, while Amgen traded at less than ten times. Here we are two years later and Amgen's stock price has outperformed Gilead's by over 40%.
Today, sell side analysts seem more enamored by Amgen and the valuations are not that far apart anymore. I am still more comfortable with Amgen because the valuation is better and I am more familiar with the company and how the stock trades. However, the valuations are close enough that I am starting to buy Gilead and reduce Amgen for the sake of diversification.