If we put humans on Mars do you think we could find the source quickly/quicker than using robots? Is it a case of the robots finding signs of life and humans confirming them and getting the specifics? I'm asking because I'm not all that informed on this but from what I can tell robots have very specific missions so may not be able to find life even if they detect the signs.
Assuming equivalent spending Robots are a much better option. But, a manned mission is likely to get ~10-100+x what unmanned missions get so it's hard to say.
Also, those rovers did a really wide range of things for their cost. From driving around 40km and taking pictures to analyzing chemistry and even testing for "wobbles" in the planet's rotation that would indicate a liquid core. Sure, they cost ~500 million a pop, but compare that to 100's of billion for a manned mission that might never reach Mars and things don't look so hot.
