Congratulations on lining up all the top options. This may as well be a rethorical question since it covers all the possibilities! Normally, based on my backgr

Congratulations on lining up all the top options. This may as well be a rethorical question since it covers all the possibilities! Normally, based on my background I'd recommend the startup as #1, the job at Microsoft as #2 and the Ph.D last. But I must say I'm not crazy about the startup you describe. Would I really advise you to join a startup I don't believe in? Failure is a great learning experience. Looking for paying customers is a lesson that neither Microsoft nor a Ph.D will ever teach you. But isn't it a little bit early? My preference is to become an expert first and then start something. You must do your own soul searching. Are you satisfied that you are "great enough" in your field yet? For some, it takes a few years of a regular day job. For others, they are great by the time they get their bachelor degree.