It all depends! Some ICOs will be more successful than others, therefore, research about what ICO you invest in is key.
It could be argued that Bitcoin has more reliability, however there could be higher and quicker gains to be had if you invest early in one of these projects.
Bitcoin has seen a rise of around +1000% within the last year but then has dropped just lately. Still a great rate and arguably less risky – but choosing the right ICO could also allow you to make some major wins.