You're getting conflicting answers because the truth is we are still kind of figuring out what is best - and it varies by household, species, and individual parrot!
The only thing we DO know is that an all seed diet is detrimental to most parrots health. Similarly, for some species like budgies and cockatiels, an all pellet diet is also not good.
Some people feed mostly pellets, with some veggies, fruits, and grains.
Some people feed mostly veggies, fruits, and grains with some pellets.
Some people go pellet free and do a whole food diet!
I would ask yourself:
- What is the breeder/current owner currently feeding?
- What is my budget?
- What do I feel reasonably able to do?
- Will I be able to get my bird outside for 30 mins a day several times a week year round?
And build from there.
First, what is the breeder/current owner currently feeding?
This is important as birds are naturally neophobic and you will need to plan to feed what they are currently feeding when they first come home. Some birds will starve themselves if they do not recognize their bowl is full of food! It also gives you an idea of what challenges you may face. A bird on an all seed diet may be more of a challenge to convert than a bird that is already eating a wide variety of foods.
What is my budget?
Some pellets are more expensive than others, and a whole food diet is going to likely be more expensive than a diet that includes pellets.
What do I feel reasonably able to do?
Obviously pouring pellets in a bowl and giving some veggie in the morning or at dinner is easier and takes less time. Doing a whole food diet takes more time to plan, prepare, store, and feed. Veggies and fruits should only be left out for up to 4 hours, which can also be a source of conflict for some schedules.
Will I be able to get my bird outside for 30 mins a day several times a week year round?
Birds need Vitamin D3, and there are no vegetarian food sources that contain it in enough abundance for our birds. So, they will either need to get it from the sun in the form of UVB (unfiltered, not through a window), or from their food. Most pellets are fortified to contain D3.
Overall, you'll likely need to be flexible and patient. It can take time for birds to come around to what we want to feed them!
As for pellet, if they are on seed only right now, I recommend Zupreem Fruity. It has been the only food all of my birds, including seed addicts, have taken to. You can always switch it later! Ideally we would want them on a dye and sugar free pellet, but sometimes we need to ease into that
