i doubt someone who TRUELY needs 1920x1200 is going to opt for a 15" over a 17". the fact you are typing on a 12" and find a 15" too big tells me already you don't actually need it, but rather want it. two different worlds, and apple tends to cater to the need rather than want crowd.
Well, you tell me which Apple laptop to get!
I travel a lot and also usually take my laptop to work and back home every day. Hence I really like something as small and light as possible. I used to lug a 15" WallStreet then a 15" TiBook for years, until my back and shoulder said "no" and I went with a 12" PowerBook instead. Since then I much appreciate smaller sized laptops.
However I work in 3D and use Maya, RenderMan and Shake a lot. So a 1024x768 resolution is totally useless to me. At work as well as at home I have a 23" monitor to plug my laptop in.
But this doesn't help on a train, or in a hotel or cafe as I can't lug a 23" display around.
Maya has a minimum resolution requirement of 1600x1200, and also needs a dedicated (preferably Nvidia) GPU. This basically rules out every MacBook, MacBook Air and any current 15" MacBook Pro.
Yet from past experience a 17" is not for me. That's too big and heavy. Definitely.
IMHO a high-end 13" laptop with 1920x1200 resolution and Nvida GPU would be ideal for me. I could still plug it into the 23" screens at work and home to get 'bigger pixels', but also have the ability to do some real work when I don't have access to an external monitor.
But of course such a machine does not exist, anywhere in the world.
A high-end 15" laptop with 1920x1200 resolution would probably be as far as I'm willing to compromise.
But I'm open to better suggestions!