Ebony is generally denser and more abrasion resistant so it will last longer and make a heavier neck (not necessarily by much depending on the piece of rosewood. Rosewood is generally more dimensionally stable and so is less likely to get 'fret sprout'. This can be compounded because most ebony is not quartersawn these days and so is less stable than the well quartersawn ebony boards of yesteryear. Ebony is also more brittle and likely to crack, but that is of very little practical concern if it is well seasoned and kept conditioned.
As others have said, ebony has greater internal dampening, so that when you tap it it does not ring so long as a very low dampening wood like most true rosewoods, but if you can tell the difference in tone on a finished guitar your ears are orders of magnitude better than mine.
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