Alibaba has been one of the best-performing mega-cap stocks of the year, surging 100%. Most recently, they had a blockbuster quarterly earnings report, and hedge fund manager David Tepper took a large stake in the company. It's now closing the gap on Amazon, another rapidly-growing tech giant. Business Insider executive editor Sara Silverstein compares the two companies, then discusses just how high Alibaba's stock price can go as it attempts to expand more into international markets — which is when it'll start to compete more directly with Amazon.