I assume your talking what type of protein is best for a lean bulk (whey, casein, egg, etc)? I personally like a blend of proteins (ideally like a 33% break down of isolate/casein/egg). However I typically buy Isolates or a blend and take it with milk or cottage cheese to up the levels of certain proteins (and thus get a steadier stream of Amino Acids in my blood and keep nitrogen retention up).