That is the question at this Oxford debate this evening (in a couple hours, sorry about the short notice).
[Update toward the end of the debate]
As I’ve noted in the past, debates like this are pointless, because they are a false choice based on a false premise. We don’t have to choose between populating Mars and saving the planet; we have abundant resources for both. The false premise is that this is going to be a collective decision whose outcome will be determined by an Oxford debate. People who go to Mars will be doing so with their own money, so people on Earth who oppose it are going to have to make it illegal to prevent it. There is a word for people like that: jailers.
Do not let the technical success of Webb make anyone think that we should have done it that way, or should ever repeat it. The future must lie in space assembly, not origami.