IEO is more popular than ICO. Last year, many ICO company generated money. They have not list their token on exchange still.
That is why IEO is more reliable the ICO. User think it is listed on Exchange so it is good. But to be honest, IEO doesn't guarantee the success of the coin.
At present, many developer teams are turning to using the IEO method instead of ICO. Besides being easier in achieving sales targets, with the IEO method, the developer team can focus more on developing its products.