Bjartey, Bjarma, and Björk all came from the same breeder who maintained full offering of ZuPreem in one dish and a Kaytee seed mix in another. We continued with that because they liked it and "if it ain't broke, don't fix it!" Bjarma never touched a single pellet her entire life, despite many efforts to transition her to them. Our vet told us his first choice was Roudybush. When we got Bjargdis, the breeder had fed exclusively Roudybush. We transitioned Björk to Roudybush and we really like it and more importantly, the girls like it, too!
The ZuPreem was good, but they picked out the different colors--green first, then yellow, and if nothing else was left, they would go for the red and orange. This made for a menagerie of poop colors and was difficult to monitor health as a result. We didn't like the dyes anyway. I see that ZuPreem seems to be increasing availability of their product line that does not contain dyes; I might have tried that if we weren't well established on Roudybush.
My biggest critique of Roudybush is the fact that they pulverize it while eating it. We sift the dish twice per day and every other day, we discard and replace with new the entire contents. We maintain full availability, but try to keep it within what they'll eat to cut down on waste. The amount lost due to sifting is significant.
We stayed with the Roudybush because of the organic line-up of ingredients and the poops are much more well formed and not nearly as messy. Ultimately, our avian vet--whom we completely trust because he is so wonderful with us and our babies--recommended it as his first choice. By no means am I a nutritionist, but even if he did not have a recommendation, I would likely be inclined to stay with Roudybush.