The moon may be much cheaper but We've been there, done that and learned most of what we can from it. Mars is the next step forward in gaining knowledge about Earth and other planets and full of new information on how are own planet has formed a the possible future of Earth. Mars could also teach us about the conditions needed to sustain life on other planets.
I think that space exploration should focus on Mars. There has already been extensive research done on the moon. There have been several moon landings over the last few decades. There has not been anything like this for Mars and I think that we have much more still to learn from Mars.
The moon itself has already been extensively covered through satellites as well as man-powered trips. Mars remains somewhat of a mystery, despite it being relatively close to the Earth's orbit. There have been signs of water and life, which opens the possibility of possible origin of life in our solar system as we know it. Perhaps Mars can be made hospitable in the future.
The moon has been explored fairly well with satellites. However, Mars continues to be a large mystery. With an atmosphere similar to Earth's and bountiful resources as well as evidence of water and possible life, it would be wiser to explore Mars' terrain and resources. Scientists may find things that would be beneficial to human beings as well as solving a potential mystery of the universe. That being, are we the only sentient beings in the universe?
I don't necessarily agree with spending so much money we don't have on space exploration, but at least if we go to Mars there are many things we can learn. The moon has already been done many times, and we have far less questions about it even if it is a lot cheaper.