IEO is more interested. Besides new investors can buy tokens directly in exchange, and can also be bought by investors who are on the exchange. In addition, the project you are running has been verified first by the exchange party, so it is trusted.
but I've seen a project that does a sales system with ICO and IEO. they don't do it together at one time. but they use ICO sales when private sale. then presale and mainsale they use exchanged IEO. I forgot the name of the project, but I've seen it.