Though the two are partly set in space, they are definitely different types of movies.
That said, which do you prefer?
Both have spectular visuals and great emotional performances, but for me, it has to be Ad Astra. There is something about the slow pace, beautiful visuals, and Brad Pitt's subtle yet engrossing portrayal of McBride that really hit the spot for me.
There's also a lot to unpack about the movies messages and to what extent they overlap/diverge.