I think the most important is for the coin or token to actually have a use case or product, otherwise, it's just another decentralized coin that you can trade and we already have them in the market.
But, I think IEO is better than ICO, because to me with ICOs there are lots of scammers and from my experience, it is very hard to prove or be sure in the legitimacy of the project.
But with IEO there are procedures a company has to go through before the launch and it kind of gives me the courage to trust these projects a bit more.
For example, the
https://yanu.ai/ IEO is trustworthy and they have a very nice Candybox campaign for token holders, a real product with a real-life use case

You said whats most important is the token or coin to have a use case or product which will influence the crypto investors and as the OP said IEO and ICO are identical. However, the procedures done by crypro exchange site before they launch a IEO doesnt guarantee the genuine of a project and does not stop scammer from scamming crypto investors as we both know that they can steal someone ID and use it for the so call procedure.
I believe we still need to verify the genuine of every IEO from crypto scammer finder like user ICO ethics before investing.