They are very similar and can often be mixed up. And to be honest, it is fair enough because there are no real definition of what a Profiterole is and how it is different from a Cream Puff. Since a Profiterole Bun is made the exact same way as a Cream Puff and they can be both filled with a Cream, I would say that for me, the main difference is that Profiterole can be served frozen (not Cream Puffs / Choux à la Crème) and that Warm Chocolate Sauce is usually only served on top of Profiteroles - not Cream Puffs.