If it is between Death Star and Coruscant, I say Coruscant. The Death Star makes for a cool scene to set up A New Hope and it looks really cool, sure, but it just raises far too many questions. Why did it take almost 20 years to build the first one when they already had the plans but they were able to completely redesign, improve, and build a new one in only like 4-5 years?
It’s unclear when does the scene take place. Sure, the next scene is Ben “delivering” baby Luke, but still the death star scene could take place a few years after Palpatine founded the Empire. As for “how long does it take to build the death star”, ROGUE ONE might give an answer ?