RE: Fight Zombies, Or Go To Mars
What a classic Geek question! It's definitely better than 'pirates or ninjas?', at least. It's a lot of fun to run through scenarios like this with friends, but there's a serious side, too - it says a lot about human nature, our instincts, and how we run through hypotheticals. On the topic of 'can zombies swim?', there's a great (read: terrifying) scene in one zombie movie (I can't find the name or the clip after 20 minutes of searching... it was a cheesy one on at 2AM on sci-fi) that has the protagonists trying to escape to an island on a boat, but when one of them accidentally falls in the water, he realizes that it IS filled with zombie... they're just walking along the ocean floor, reaching up to pull him under - but then I guess it depends on which flavor of zombie fiction you subscribe to.
How we're setting up the premise, which version of the ideas we're using, has a lot to do with this question, doesn't it? Are we talking Romero-style slow zombies, or some of the crazy things that can run on walls like in Resident Evil? When you say 'Mars Colony' is there anything already there, or are you building the mars colony? The former gets into more sci-fi questions (after all, Mars colonies can't really exist anytime soon)... the latter makes me want to take my chances with the zombies. I don't even know how to grow food on earth. I don't trust myself to try it on Mars - nevermind whether the mars greenhouse, etc. is even possible.