I used to use those when I was younger and did notice some improvement with them. At least in terms of strength and size. They're gonna help you bulk up though which might not be what you want if you're after definition. Also, if they taste like cake that probably means they have a lot of sugar which can turn into fat if you don't burn it off. Extra fat will rob you of definition really fast. Think about most power lifters. they just look big, some even fat, but don't have that ripped look that most people are after.

If I were you I'd stick to more natural protien sources. Like others have said eggs, tuna, chicken breasts, that type of stuff. Also get some complex carbs in your diet. They'll give you the energy to lift more. A tuna sandwhich on whole wheat breat is probably a lot better for you in the long run than any protien supplement.