It depends ones perception towards a project. There are projects with great fundamental, coordinated financial expert and team with great vision.When you invest on this project before the ICO,after the lunch on exchange, the price might go down below the ICO,but with time the price of that coin might skyrocket to the extent that early sellers will start to regret selling their coins.
This normally happen when the product is fully lunched.
This also happen when the product has gain massive adoption and real usage.So,investing on ICO before the lunch or after the lunch depends on how the investor see the potential in the project.