As has been said the drawbacks to the MDR are:
Limited hours, you need to be up early
Relatively relaxed (meaning slow) service. A complete breakfast is an hour commitment at least
My experience of the food itself is that most is the same “quality” as the buffet.
Advantages are:
You are being served.
You can somewhat customize your requests
They come around with breads/pastries and serve them to you
The coffee seems better than buffet coffee. Same as after dinner coffee
You can more readily get an Irish Coffee etal for breakfast 🙂
Drawbacks to buffet Breakfast
At peak time it can be challenging to find a table (especially for 4)
The “regular” coffee tastes like syrup coffee which is not to everyone’s liking
If you are by yourself you need something to “preserve” your seat if you get up to get anything like a glass of water or whatever
Advantages
You can get made to order eggs and omelets delivered to your table
People come by and offer you juices and coffee and tea
You can be quite quick
Great place for variety including fresh fruit of your choice, bagels and lox, and as much bacon as you want…….
We usually try the MDR breakfast maybe once on a cruise and when we are sitting there after almost an hour still waiting for our main dish, we kinda wish we hadn't. It is much more leisurely and in my experience slower than lunch or dinner. We don't usually order room service breakfast because… who wants to be woken up if we happen to be sleeping.. But that's us.