Another diference in protein powders is how good your body can absorb it. For example whey proteins absorb very quickly which is what you want right after your workout. Egg, Soy, and
Casein are absorbed much more slowly than whey...
Even among whey proteins, there is difference, you've got hydrolyzed whey, ion exchange whey, micro flitration wheys and cross flow microfiltration... Long story shot, you, as a bodybuilder should be looking for hydrolyzed whey protein which is absorbed by your body the quickest.

You be the one who decides.