If ICO wasnt been plague by scammers acts ICO will way better than IEO, ICOs are programmed to run on the projects very own website and no any third party involvement at all so any fund raised will go directly to the dev or project team, no loss of funds to scam exchanges,after some successful IEO fund raise on some exchanges they dont bother to send the funds back to the project teams
ICO projects are not as good as you would expect, some investors will be more interested in IEO, because with IEO, investors have a guarantee that the coins or tokens will be listed on a definite exchanger.
without a third party the DEVs of an ICO will be easily tempted by the funds collected from investors and become scammers without a plan.