It depends on what the difference between high and startup salary is. Some startups which are well funded are offering generous salaries to start with. It is difficult to predict if a startup with be successful or not, but if you really believe in the idea, are excited to join the startup because of the problem they are solving, I suggest take a salary and some equity. If you are not really excited about the startup's idea or their product and just want to work there as a job, then take the high salary