I think they're fairly comparable if you're only looking at staff attacks, but if you use any of the staff abilities on your bar, destruction staves will clearly be the better choice for pure damage.
I feel like resto staff itself dose more damage, because it's not a elemental damage type, and I have no idea what damage type it is, and you can add other damage types too it
I could only see resto 'doing more damage' if you were only using class/non weapon skills that cost magica, and using the heavy hit to return it (thus allowing you more skill usage).