Although I possess a 730,I honestly have to tell that the 640 surpasses the 730,it has glance screen,Lumia Moments,13mp camera with Zeiss optics,bigger battery.Not to blame the 730 because it was launched at a different time scale,if you are a avid fan of Nokia then you can buy on of its last Lumia phone.But personally using a 730 I would definitely tell you that buying it is a good investment.