Well, Project Orion was certainly more dramatic -- detonating hundreds of nukes to punch a rocket up into space. It was also top-secret at the time; that explai

Well, Project Orion was certainly more dramatic -- detonating hundreds of nukes to punch a rocket up into space. It was also top-secret at the time; that explains its mystique. As far as being a superior choice, I don't think it's quite apples to apples. Project Orion (nuclear pulse propulsion) was designed to get very large payloads directly into orbit. Nuclear thermal rockets like NERVA were apparently designed to be used as drop-in replacements for upper stages on conventional chemical rockets, or as space "tugs" in orbit. That might imply that it was difficult to design a nuclear thermal rocket which would deliver the high initial thrust(?) necessary to lift a payload directly out of our gravity well (but IANA rocket scientist, so I may be mistaken on this). That said, a small blurb on Wikipedia does mention that "Robert Bussard proposed the Single-Stage-To-Orbit "Aspen" vehicle using a nuclear thermal rocket for propulsion and liquid hydrogen propellant[...]" -- so maybe it would indeed have been a superior design choice in the end.