IEO are not totally safe, but they are just safer then ICOs. I mean they got backing by exchanges means that they have an extra layer of security which ICO lacks. So they may be better then ICOs but they still are not a guarantee of safe investment.
IEO has more certainity for investors that playing fast.usually there are investors that joined in IEO and then they immediatly sell their token to swicth assets and participating in other IEO or projects.