While making an investment into bitcoin, it gives the assurance for the return from the investment. The same is not possible with the investment made on ico. If the particular ico grows big in value, the user will get benefited big than that of the earning got on investing into bitcoin. In short investing upon ico is much riskier than investing into bitcoin.
Both are positive things but, in icos, you can make more money if you get into the right one. In bitcoin, the rate of profit would be lower clearly.
The advantage of bitcoin is less risk compared to icos.