MSR - Thoughts on Pure Research Vs. Human Survival needs

For a Mars Sample Return mission what would be the major differences between the needs specific to the success of a human presence on Mars and the desires of the scientific community? Would a diverse sample from a wide variety of areas or an in-depth set of samples from an area that is currently thought to be best for human survival? What else should a MSR mission try to accomplish besides returning a sample? What do you feel the costs of this type of mission should be? What justifies your estimate?