I can't say I've ever even heard of Nutribird, much less used it. Pick up a bag and compare the ingredients, see how it differs from the Exact. Most are based on corn, wheat or soy, with wheat being the preferred but none being perfect.
Personally, I don't think pellets are a great diet for parakeets, anyway. The high level of artificial ingredients in pellets has been implicated in causing gout and liver & kidney problems in, well, all birds, but most frequently parakeets and cockatiels. Pellets are cooked at such high temperatures that most NATURAL nutrients are cooked away, and the artificial replacements are not as easily absorbed by the body. Additionally, pellets usually have too high a percentage of protein for parakeets which would naturally eat grass seeds, which are quite low in protein. In my experience parakeets do much better on a seed-based diet, including sprouted seed, with additional fresh foods (esp. dark leafy greens).
Here's a good food pyramid for grass seed-eating birds, for rough percentages:
http://www.holisticbirds.com/Hbn02/autumn02/images/fptiels.gif
BTW I'm not just spouting information I heard from someone else; I fed pellets for many years, but over the past 1-2 yrs have been gradually increasing the amounts of other foods, especially sprouts and vegetables, and my birds look & act MUCH healthier. I may stop using pellets altogether, they don't seem to add anything worthwhile to my birds' diet.
Price-wise I think I spend less now than I did feeding pellets. Some of the foods cost more, such as the fresh produce, but others cost less -- such as the seed. I use a very plain seed, non-vitamin-fortified, for both sprouting and feeding dry. They get their vitamins from the sprouts (which are much more nutritional than dry seed), leafy greens, and other fresh foods.
I started lowering the amount of pellets because I lost one of my favorite 'tiels to visceral gout, which I discovered is frequently caused by a pellet-based diet.
- Lara