Sci-fi role playing games have been around for a long time and I have been a fan since I first found the Traveller box set in the 1980s.  A few decades later I found myself caught up in the Starfinder release by Paizo and ran a year of Starfinder Society play.  I found that both systems had strengths and weaknesses and may appeal to different groups of players.

Starfinder is a science-fantasy RPG that is based in the Pathfinder universe.  The game is very much a mixture of science fiction and fantasy.  There is magic in this game and hi-tech.  It’s a neat game with many interesting stories.  I found it to be a little too fantasy and the rules seemed to be focused more on role playing and less on depicting sci-fi worlds.  The planets descriptions don’t include gravitation constant or air pressure or atmospheric composition.  I think this stems from the Pathfinder roots of the game where fantasy characters don’t leave the planet and never have to contend with three times normal gravity or an atmosphere that’s mostly ammonia.   If you like role playing in a futuristic setting using a familiar ruleset that isn’t over loaded with science then Starfinder is a game for you.

Traveller is a much more realistic sci-fi role play game with actual physic equations in the book for interplanetary travel.  The rules support all the realities that Starfinder glosses over.  There is no fantasy, no magic, and no pantheon of semi involved deities.    I think the challenge for new players is the dearth of materials and editions and meta-plots.  I tend to play RPGs in localized settings and situations and original Traveller lends itself to this as well.  The Imperium is always a large impenitrable backdrop in my games that players don’t interact with directly unless they are dealing with government issues.  Akin to how I deal with the the DMV in real life.  The universe in Traveller is giant, but since communications travel at the speed of spacecraft you can have local and isolated places that follow their own rules and social norms.  

I like both systems.  I enjoy Starinder when  want to play Pathfinder in space and when I need a more crunchy science fiction adventure I head for Traveller.