in short ieo is less riskier because you will know if what ieos are good and bad if you will only based on the exchange listed by them ~~
With so many pump-dump on exchanges after fundraising, I think both IEO and ICO are the same, both are high risky. The success of investors is not only measured by the success in fundraising or in listing on top exchanges. But when the token values can be growing constantly on exchanges. At least, the volume is rising properly, it indicates a good interest from people. Unfortunately, after fundraising, most token values are gradually losing their values on the market currently.