DF is at a much more completed state. The play hours to see "everything" is around 2k hours played, cuz the interactions in the game go deep and players can find more cool things to do way after. Conversely, DF is also near a dead end in development, only thing would be animations, better isometric, readability on happenings, all of which is baisically near impossible at this point.
While starsector has a well developed combat and... That's it. All the other aspects could be improved so much more that honestly, unless some real life events force it, doesn't make sense to release it. A player realistically can pkay about 12 hours before exhausting most of the stuff to do.
You only get to release a game once. Release it now, get 1/10 of the people when you release at 20 years. Anything artistically creative reap more benifits the "deeper" it goes untill a certain completion point. Starsector is faaaaaarrrrr from that point.