Desktops are not portable.
I wouldnt call this thing that portable. Portable would be anything that you can carry with ease, such as the MBP or any laptop I would say less than 7lbs. But everybody has their own view on what IS portable, so that would be your decision.
All I know is that when I am going somewhere on vacation, I want something that has enough power for what I do, in a small package that is thin and light in my backpack. The MBP/MB is the perfect candidate. Nobody wants extra weight...
But, everybody has their own opinions, so do what you want.