creatine isn't a protein
it has the effect of drawing in water...
this effect can allow you to obtain larger muscles...
it also helps to supply energy to muscles, allowing you to lift longer...
some think it has bad side effects....others do not
I think it is completely safe
and I am a believer in soy protein...it's a plant protein, lol. Nothing miraculous in it. Just like tofu. Some people hate it, macho guys I know hate it...for no other reason than it's not meat.
There is no real intelligent reason to not take soy protein. However, for bodybuilding sake, red meat protein has the added benefit of enhancing testosterone...so take it as you will.
I just happen to be one of the least macho guys you'll ever know.
When I lifted hard and natural (and vegetarian), it is near impossible for anyone to obtain the same arm size I had without steroid enhancement. That could be genetics as well. There's no exaggeration there...but if i let my arms hang limp and no flexion, they were about 2 inches bigger than a 2 liter soda bottle...that's pretty good for a natural vegetarian bodybuilder...and only 5'9".