I think that a new mission to land on the moon would be good for scientific research. Not only would it be good for scientific research, but it would also be good for getting people interested in the subject again. We can always use more research into any subject, and a moon landing is no different.
Considering the population growth that we have on Earth and also considering questionable environmental policies around the globe, I see no reason why we should not be landing on the moon and doing more research. Hopefully its much later rather than sooner, but eventually we will be forced to colonize both the moon and Mars and maybe even more.
Indisputably humanity's space programs need a boost, a spark in interest from the general public. Either of these should server that purpose but Mars would have more scientific potential. We have been to the moon and collected samples and put experiments. It would be worth our time to go back but given the current financial restrictions to space exploration at the time we can only pick one for the near future and we haven't been to Mars putting it above the moon, it doesn't cost a whole lot more, and Mars has had running water and there is evidence it once looked like Earth does now. To me this makes Mars a logical next step in human exploration.