Disadvantages:
They tend to be highly processed and high in saturated fat so have less nutritional value and are High GI so don't keep the consumer feeling full for very long before they must eat again.
They don't tend to work out very cheap compared to vegetables and meat either.
Advantages:
They're quick and require minimal preparation, especially if one is exhausted or in a rush. Frozen meals are great for taking to work and one only has to wash a fork or spoon afterward. Kids eat them.