Well, since I'm not a native English speaker so I'm not sure but:
*Mandarin has similar words order to English than Japanese. I don't know korean.
*Japanese doesn't change its pronouncement even if it is connected after or before other words.
*Tence and character difficulties are almost the same.
...that's what have come up with me for now regards of learning difficulties between them.
I'll add more when I remember other points.