Protein is the only macro that has all 4 amino acids (carbon, hydrogen, nitrogen, and oxygen) so either soy or whey would be a good choice if you need more. The main difference is that soy protein is derived from plants and whey protein is derived from cows milk.
Here are a few comparisons of their biological values...
Whey has a higher NPU (net protein utilization)
Soy has a twice as much Glutamine (for building muscles) and Arinine (for physical fatigue/mental health).
Whey has a higher AAS (amino acid score) at 1.14. Soy's AAS .99. Anything over 1 is considered more than any person needs.
They have the same protein digestibility corrected amino acid score (PDCAAS).
Most think that for bodybuilding whey is better but seeing all the vegan bodybuilders makes me think it is more of a preference so just use whatever one you end up liking best.