After the huge number of scams that were in 2018, investors have gained a lot of experience and now they are rare invest in ICO, preferring to invest in IEO.
Now there are a lot of scams too and conduction of IEO and listing on the exchanges does not guaranty the success of the project and raise of the tokens.
I think it all depends on what kind of exchange IEO will hold and how popular this exchange will be. I think if one of the popular exchanges to confirm the listing of tokens in advance it says a lot.