I bought the base 11, because primarily of the footprint. The way I see it, if I am going to buy a 13 inch Macbook, it might as well be a full fledged Macbook Pro. 2 pounds are not going to make a difference, for me at least.
I also tried to choke up my base 11 and have not been successful. Opened every program I have, Safari with multiple tabs, Youtube running HD, and the little sucker was still snappy. Therefore, for me, I do not require 4gb of ram. Perhaps if you try something heavy tasks then 4gb will be needed.
The smaller foot print of the 11 is its biggest advantage. I go through my class nights while riding a crowded NYC subway train in the morning. It is easy to hold in one hand, similar to an iPad.
My only complaint is that everyone wants to hold it and wave it around.