In my opinion, IEO is not for crypto startups that are seeking funds to kick start their project but for projects that have raised capital already or have rich advisor and team to fund the project. Fund-raising through IEO can be very challenging for startups that need money to kickstart their project, because they will need large amount of money to conduct their tokensale on good exchanges, as this exchanges only list projects that meet their legal requirements and can also afford to pay their listing fees. So the best means to raise money or capital for new projects is to present their proposal to Venture capital firms or Angel investors.
I think ICO and IEO are the same thing and the different is IEO administered by exchangers. Sometimes, if you are looking carefully, there is an ICOs from a company and want to build new project, its not a start up.