Your breakfast choices should be based on your insulin sensitivity, as well as other factors like training time and your last meal from the day before.
Two of the most muscular guys I know eat a lot of food and overall carbs at breakfast. An IFBB pro friend of mine has two bagels along with his eggs in the morning. A strongman friend of mine must have 2500 calories at breakfast and it includes about 300 grams of carbs from oatmeal.
Personally, if I eat that I will fall into an insulin-induced coma! Not to mention that I train very early in the morning, so eating that much food would make it impossible for me to have a decent workout.
The most important thing is to have a source of rapidly absorbed protein in there. Eggs (if you tolerate them) are likely the best choice. And you need some yolks to maximize growth and overall health. If someone is trying to gain maximum muscle, they might go with 3-5 whole eggs. And if they're leaning out maybe one whole egg along with 6-8 egg whites.
Since I train really early in the morning (I wake up 4:30 AM and train around 6:30), I want something easy to digest. I also don't take in carbs because I'll have carbs in my workout drink (Plazma™). Also, I have carbs in my last meal of the evening to help me relax and shut my brain off, so my glycogen stores aren't empty in the morning.
So what I like to do is make a protein pancake:
- 2 whole eggs
- 2-3 egg whites
- 1 scoop Metabolic Drive® Protein
- Cinnamon (about 5g)
Mix it all up and toss it in a pan.
I also drink 12.5g of sodium bicarbonate and will have a small amount of veggies just to lower the acid load of the meal. Easy to make, easy to digest, plenty of protein, and the cinnamon helps with insulin sensitivity. If I were not training as early I'd add almonds for more sustained energy.