I chose un-manned missions.. why?
While i'd love to see more exploration of Mars and the moon etc by astronauts, where some real science can be done, it's going to be limited.. i just can't see them sending astronauts any further because a) there's nowhere for them to land and b) the radiation would be a killer.
So it means pretty much the moon and mars.. I'm sure there's still heaps to learn about those planets and satellites, and that of course will help us understand how Earth came about, but I think more can be learned by the robotic missions to other places, such as venus, mercury, jupiters moons, titan again, etc.
Add to that, the manned missions are more of a logistics nightmare, because so much more care has to be taken because you're talking about losing human life if something goes wrong, as opposed to just losing a robot or spacecraft. Just look at the Discovery shuttle, how many times it's been delayed to do upgrades for safety etc.
On the flip side, manned missions to the moon to start setting up a lunar base, mining for water/air etc, setting up a telescope on the moon

would be way cool and could easily swing my vote the other way..