If you are sure in the project, it is better to buy tokens on the stage of ICO. You will get privileges and manage to use them further. Sometimes, it is senseless to wait for the dip.
Of course, you speak correctly, but this should be done taking into account the market trend, which is similar to the situation of 2016 or 2017. But today, all the privileges of new projects of ico companies are almost nothing compared to what prices are after listing on the stock exchanges. Many investors prefer to invest and buy coins on stock exchanges, rather than on time the company ico.