There's no much difference, but when you conduct IEO in a reputable exchange it means there are legit, especially in Binance as they are really doing their best for them to run IEO with those legit only and no scam, but in ICO, you cannot determine who are scam and not because scammers are also clever enough.
i think if ico will also be conducted by famous people , it cant be also turn into scam because these famous personalities are going to get affected if they scam the investors . that is the same as putting an ieo on binance because binance are also afraid to get a complain whenever the ieo turns bad . if that would be the basis , both ieo and ico are equal but if that isnt the condition , we should have choose properly and grade them depending on thier performance