Although the GT 840m is a newer card it is both bandwidth limited and crippled with ddr3 memory and was designed as a mainstream card for 1366x768. The gtx 760m however is designed to play games at high settings at 1600x900 and a gaming card. The larger memory bus and faster gddr5 will make it much faster than the GT 840m not to mention more shaders despite being Kepler.