I think it depends on the conditions and potential of a project. if it has good potential in the future, I think it would be better to buy it at ICO, because at ICO usually the price is quite cheap, especially when there are usually bonus programs or price discounts.
it might be a good choice to buy in ico. but we have to be more detailed and accurate in ico, because now ico is a lot of scams and I prefer to buy ico coins that have been listed on the exchange and are still of low value, it could be the best solution.