you should only invest in what you can predict and logically say it has a lower risk. it doesn't matter what it is. it can be an ICO or it can be an altcoin or anything else.
so far ICOs are the most unpredictable of all. which means investing in them is always going to have a much higher risk than investing in an altcoin which has already been around for a while and also has some charts which you can do additional analysis on.