I happen to have these two headphones and I don't really hear any similarities other than the fact that they make music.
Seriously, they're pretty much opposites. The overall sound of the iM716 is thin, even when amped, while it would be impossible to describe the O2 as thin. The O2 bass extends very deep, while the iM716 does not. The O2 has a good soundstage, the iM716 does not. I could continue like that, but it's really an apples and oranges comparison. The iM716 are great because they provide isolation and a decent SQ at a good price, but other than that they don't rival with the big boys.