I also think IEO is better even if all are similar, and the main advantage is as already people say the listing on an exchange because there was a lot of ICO who not get listed on good trade volume exchanges.
IEO has proven to be the most profitable base price comparing to private sale prices ive seen recently, which is why i hope to be lucky enough when Tokoin.io announce their upcoming IEO to get in. This hidden gem project is not one to miss, they will take the MSME market by storm which in itself is humongous.