There is no real advantage of using one over the other, in c++, the only difference between a struct and a class is the default visibility of it's members (structs default to public, classes default to private).
Personally, I tend to prefer structs for POD types and use classes for everything else.
EDIT: litb made a good point in the comment so I'm going to quote him here:
one important other difference is that
structs derive from other
classes/struct public by default,
while classes derive privately by
default.
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