I think the Grand Seiko is much more unique, and a better quality watch due to its finishing and movement. I am referencing the models such as the Shunbun or snowflake.

However, the aqua terra truly can make a one watch collection and I believe it to be more versatile. So it depends, will you get more watches in the future? If so the grand Seiko, you can make that the classy dress watch or casual daily. But the aqua terra can be dressed down easier in my opinion.