Mine all have taken to Roudybush really well, even a 14 year old stubborn seed eating tiel, and I personally quite like the brand. I got hooked on it when I lived in Orlando, the shop owner I worked for had been feeding it for almost 10 years exclusively and had a lot of success. I, personally, don't believe in serving only
pellets... how would you like to eat a bowl of nutrient complete cheerios every morning? You're getting all you need
but do you enjoy it at all?
I think, whether you feed pellets or not, as long as you are comfortable with the brand and can stand behind it, then go for it! There's no perfectly right way to feed your parrot. Everyone has their own idea on exactly what is right and it varies from vet to vet, region to region. I've used both Harrisons and Roudybush and prefer the Roudybush. I honestly feel Harrison's is overpriced, but it is a very good brand and you should feel totally safe feeding it to your bird as far as quality goes.
Personally, I feel as long as you supplement the pelleted diet with quality seeds, veggies, and fruits you'll do just fine
Zupreem is a good brand. Think of it, in terms of dog food. Zupreem is your Eukanuba, Purina, etc. Good quality, not perfect but something you can feel confident feeding your bird. It's not like some yucky Walmart brand or full of dyes and such.
The highest quality, from what I've heard, and best rated are Roudybush, Harrisons, and TOPS. As I said, I think Harrison's is overpriced and I have no personal experience with TOPS, but everyone I know who has used it loves it. Research ingredients, benefits, etc and see what fits your personal belief as far as nutrition! Some people think all organic is the only way to go, others think natural is good, etc. If you would feel comfortable eating it yourself, then it's good enough for your bird!