IEO and ICO of these days are almost the same thing and I would say what differentiates them is the exchange. Some exchanges do not even sell coins successfully and listing they ends up not listing according to IEO rate or list with IEO price which before investors could wait for little profits, it will dump on them. A successful and we'll trusted IEO has to come from a reputable exchange if not both ICO and IEO appear samething. I have seen many failed IEO and failed ICO so they are amsot same to be except the exchange IEO is being listed could help make it worth buying.
They are the same, but at the same time they aren't. Both are for one purpose, organized sales for gathering funds for the project, it's how these two are the same.
The organization of sale is what makes the difference! In some way when trusted exchange runs the sale and after token gets listed it's like an easier option, with ICO's you never know will they get to some exchange in the first place!