Just thinking about SEO this is a very good question. My personal opinion is that I would pick the third option, try and get 50% of those 49,000 a month and from that be able to build a platform where you get traffic not just because of your name, with links going into your site (perhaps using the first term's wording) you could become a competitor in those other levels.
Are we to assume those that the three choices all make good marketing sense if you ignore SEO, do they reflect the brand/product/site well and would humans find them all easy to type and remember?
If, for example the third option was just a really weird spelling of the first example with another word added to the start or end then there is a reason why so few people search for it each month.