Travelling in the Tardis would be immense fun, all of time and space and the huge variety of adventures that have been shown in the last series, lots of fun, its great. However, I'd travel with Spock on the Enterprise, not only because of the apparent abundance of alien poontang available, but because the advances in technology and the adventures you had are tangible and the result of human ingenuity, nobody back at home will think you're crazy when you talk about traveling the universe when Spock shows up with the scrapbook. The Doctor is awesome and I believe he genuinely loves humanity, but he goes around like a god picking people out of their boring lives seemingly at random and gives them a great time and then drops them back in their own time with nothing left but their boring lives ahead of them and the lingering doubts that they are in fact insane, theres no way to relate to that kind of nigh all powerful creature, its just too alien.