Another big difference if you have a two bedroom is that a dedicated 2 BR has only one entrance door from the hallway in the area of the Kitchen. This could be important if you have children and want to make sure they don't get out into the hallway.
In a lock off, there is an entrance door in that location plus one more into the adjoining studio. You also have all of the other amenities of that studio, like a second microwave and coffemaker.
HBC