i have been wondering the same thing... but this is what I have found...
Pros:
1) Separate entrance so people can come and go without bothering the main living area. This IS great if you have people sleeping in the living room
2) You get an additional microwave and little fridge.
3) If guests are not staying as long as you, you can release the studio part, and not have to move rooms for the rest of your stay.
Cons:
I believe a drawback is that the second bedroom is a studio, which means that rather than have two regular queen beds, you have a queen and a pull out bed.