Well as many will suggest diffenent things almost any pellet you can get is better then an all seed based diet or junkie diet. So zu preem, roudybush, Harrison's, top, kaytee, pretty bird, browns, higgins(they just made a pellet and it is a great hit, very nice natural sources in it), lafebers..Those are most of the ones I can say I've seen used and like most of the ingredients in.
Just make sure when buying pellets you get apprioate sized and so on, personally I use zu preem, pretty bird, some Roudy and Harrison's. Then a Higgins seed mix and fresh foods plus In she'll nuts.
My macaws eat those pellets, a lot of fresh fruits and veggies, eggs, chop mixes, bird breads the list goes on, the Higgins sunburst macaw mix and then they also get a I shell walnuts/almonds/hazelnuts and pistachios