I mostly use the term "bellydance" for the same reason as mouse: if I call it Oriental dance or raqs sharqi, no-once else except for bellydancers know what I'm talking about (I even doubt if all students in my group know what "raqs sharqi") means. I probably would be more correct to call it Oriental dance as this is a correct translation of "raqs sharqi". (But honestly, I don't think countries like Morocco are that Oriental
)