nix-shell for GHC development

shell.nix

# This was only tested against revision ac2d18a7353cd3ac1ba4b5993f2776fe0c5eedc9
# of https://gitlab.haskell.org/ghc/ghc
let
  nixpkgs = builtins.fetchTarball {
    url    = "https://github.com/NixOS/nixpkgs/archive/7e003d7fb9eff8ecb84405360c75c716cdd1f79f.tar.gz";
    sha256 = "08y8pmz7xa58mrk52nafgnnrryxsmya9qaab3nccg18jifs5gyal";
  };

  config.allowBroken = true;

  pkgs = import nixpkgs { inherit config; };

in
  pkgs.mkShell {
    nativeBuildInputs = [
      pkgs.automake
      pkgs.autoconf
      pkgs.python3
      (pkgs.haskell.packages.ghc902.ghcWithPackages (p: [
        p.alex
        p.happy
        p.haddock
      ]))
      pkgs.sphinx
      pkgs.texlive.combined.scheme-small
      pkgs.gmp
    ];
  }

Is there a reason to use this over ghc.nix?