Are you using soy isolate or soy as a protein source? Whey Isolate trumps soy and casein regarding muscle protein synthesis.
I prefer isolate over concentrate and blends.
I do use Beverly International's protein powders (essentially a blend of medical grade protein), more as a meal replacement due to the fat content and egg protein. However I prefer isolate over anything. Especially pre, during, and immediately post workout.
Advantages of whey isolate:
~contains beneficial sub-fractions of whey such as beta-lactoglobulin, lactoferrin, and alpha-lactalbumin.
~higher protein content per gram of substance.