Well I mean look at the docs. To each their own but I find Guile much more palatable than Nix. Moreover, I would rather spend time learning Guile than an obscure language like Nix. But for you Nix is a perfect DSL so i think we would probably be bashing our heads against the wall debating which is better.
As regards macros, Guile allows you to write your own macros in a pretty straight forward way that is just not the case in Nix
As regards macros, Guile allows you to write your own macros in a pretty straight forward way that is just not the case in Nix