Both ways are equally good. However i would put it on the id itself as :hover does not work on ie6 or below if element is not an anchor. If you do not care about older versions of IE. Then both ways are correct.
They are both the same, provided you always want the pointer there, reguardless of hovering.
The :hover pseudo class will inherit cursor: pointer from its non hovered state.
I would prefer to put it on the normal selector, rather than :hover.
Compatibility: IE6 and below only recognize the :hover pseudo class on a elements.