Performance is equivalent in both representations, but the important thing is being able to write

  vec4 c = a * 4 + b;

instead of

  vec4 c = vec4_add(vec4_mul(a, 4), b);

i.e. infix vs postfix order, with simple * and +/- operators etc. I would very much like to appeal to the Zig authors to see the beauty in the former expression compared to the latter, for a huge class of real-world mathematical applications.