I guess this topic has been discussed many times, to me all are the same, it is just an upgrade as far as am concern. Investors have lost hope in ICO, so dev and team coming up with another way of attracting investors in the form of STO and IEO.
How come all of them be called the same models if they are upgraded forms of each other? I do not think they are all same and this is because a flaw in ICO was covered by STO which had been more compliant to regulations. IEO have been yet more successful for their exchange deal with the fundraising and not the project team which focus on the project improvement.