i have both on hand at home. although i am a firm devotee to food intake. the only time i take in shakes or meal replacements is if im in a bind or a hurry and no time to make a meal. which happens on rare occasion. but i prefer the meal replacement over the protein because of the overall nutritional value

I use a protein powder and a meal replacement powder.It's just way easier to get the calories I want.The meal replacement shake is better nutrition wise than the protein powder.I usually include the protein powder drink with a meal.I eat pretty clean and to get the calories from one shake would be like eating 5 cans of tuna in one sitting.I just can't do it.I also mix all my shakes with whole milk.

Meal replacements are typically a more compete nutrient source rather than simply a quick protein source. If you're diet of whole foods is sound and your hitting your daily macros and micros, then it really shouldn't matter. Meal replacers tend to be a little heavier and thicker than simple protein shakes, giving you more of a sense of fullness and a slower rate of digestion. This can be beneficial if you're running a strict cutting diet.