It is always best to get a great variety of different food sources to get the widest variety of vitamins, minerals and nutrient profiles.
It's kind of nit picking but if you have the time to prep BOTH rice and potatoes instead of just one or the other for your meal, that is always better. It also keeps your meals more interesting because you aren't eating the exact same thing over and over.
What I like to do is mix protein sources. Instead of eating 8oz of chicken or 8oz of fish, I'll eat 4oz of chicken and 4oz of fish. You get two different amino acid profiles that way.