HOUSTON (Reuters) -Exxon Mobil's investors now prefer the company use its share price and financial might to acquire existing oil and gas production rather than spend on drilling that could take years to pay off. In the last four years energy investors have dumped stocks in oil companies that boost capital spending, favoring higher returns over spending on costly, long-term new projects. Its talks to acquire Pioneer Natural Resources, the No. 2 Permian shale oil producer, for $60 billion, signals it is ready to pay up for production after missing its own output targets in the Permian.