Definitely Starfleet.
I get to meet aliens, play around with replicators and the Holodeck, and live in a near utopia. That beats living with a bunch of magical racist fascists in a cold and dreary castle any day.
Although the science of Star Trek is mostly made up, I'm sure that *some* of it has a basis in reality, so I'll make sure to bring back as many text manuals about how to construct replicators, spaceships, the warp drive, etc as I can.