Projects assume that the value in the business case will occur and lock the scope early. But products require customers, and customers are unpredictable. 

Product teams are responsible for outcomes so they need to test assumptions with customers continuously and adjust track when new insights occur.  

Projects assume that separation of roles with detailed handovers is the most efficient use of expensive resources. But if you get the scope wrong up front then the impact multiplies. 

Product teams work together with quick feedback loops to limit the impact of mistakes or miscommunication early and avoid unnecessary rework later. 

Projects remove the ownership of the product and code. Deadlines force people to cut corners and because people jump from one project to the next these fixes never take place. The resulting product, design and technical debt slows down delivery over time.

Product teams own the product and are responsible for continuous delivery. This requires a focus on paying down debt regularly to ensure sustainable delivery.