As long as no one was in a rush, and such a large quantity of water were available, I’d start with Venus, which is very nearly the same diameter and mass as the Earth.
How do you neutralize the sulfuric acid?
Venus does have the advantage of having enough atmosphere if we can make it non-toxic. But we need a way of trapping the sulfuric acid. Maybe a designer bacteria, that can survive the high temps and the acid?