Which is better and why? The quick answer is whole food, we've been eating it since the beginning of time.
Now, for a bodybuilder, both are necessary. Overall, you want to eat clean whole food. I'm not going to get into what's clean and what isn't. At other times, you're much better off with liquid nutrition, such as immediately after your workout or upon waking up. These are the two times of the day I always, always, always have liquid nutrition. I want the fast absorption and ease of prepartation. When you've been sleeping all night and wake up, you want those nutrients in your body ASAP. Hence, my morning oatmeal and protein breakfast. Post workout is for obvious reasons. I have my postworkout drink immediatley after working out (combination of CFM whey, hydrolyzed whey, dextrose and maltodextrin) and have a solid food meal an hour or so afterwards when I'm hungry again.
Think convenience and efficiency when it comes to protein from either source.