For young and growing rats I do like the Mazuri. It's popular among commercial breeders because it promotes fast growth and supports breeding and lactating rats. Most likely the Oxbow may be just as good at about 4 to 5 times the cost. With senior rats that aren't eating properly the Maxuri works pretty well too. The Oxbow adult has lower protein levels, but your rats are going to eat a lot more of it... and they will get just as fat.
To be honest, mostly our rats prefer leftovers and whatever they can dig out of the kitchen trash. My wife has digestive issues and eats mostly a tasteless vegetable stew unfit for normal human consumption, but the rats absolutely love it... I leave some rat food in the dish, just in case we forget to feed them otherwise. I top up the dish every few months.