For day to day use, what are the benefits for gnu guix? From it’s website, what I could understand is it provides installation of different version of the same package, similar to rbenv or conda. Apart from this, is there anything else that will be considered useful over something like aptitude?
Reproducibility, just like Nix.
You can be certain that, if you've managed to get a piece of software running with Guix, you can also get it running identically on any other machine.
Except if nvidia cards and embedded systems are involved. Then whether you get it running is still a gamble.