It all depends on the market cycles. When the market is up - it is more profitable to try to enter an ICO and to get certain bonuses for early birds. When the market is down - most coins and tokens upon listing on exchanges are traded far below their original ICO price, which makes it more profitable to pick them up on exchanges 
I think it all depend on the project, there are some project that one just need to enter into to it before it hit the exchanges because you can not get it less than that current value.
I have enter Nebula AI ico, orhers I will wait and see the price on exchanges.