Deffinetly the porch.
We built a cabin a year ago and its only like 14' x 16' then we have a 6 foot porch, but it is still a great cabin.
We added in a sky light and lightens up the cabin ALOT.
heres some ideas for you....
(note: some time in the summer we are gonna be painting the white tin a greyish-brownish type color so it matches better.)
Outside
Inside
We have 5 windows.. theres windows on the north,east,south, and west side, and then the sky light.
We wished we had closed the floor boards closer together. If you went there and looked straight down you could see a little gap, a really tiny one. It lets alot of air in and it makes the floor real cold and it makes it a little cold inside. What you could do is lay the main floor down and then go under it and place ply wood under it, that will block most of the air movement.
http://huntingsphere.exofire.net/videos/vid3/video.php(a short video of my hole cabin, and the surroundings)