This summer, I'll be flying Alaska Airlines from Seattle to Fairbanks. A coach ticket will be reimbursed by my company, but a first class will not be reimbursed. However, if I pay the difference between a cheapie coach fare and first class (I know it's expensive but I'm willing to pay for it or turn some partner frequent flyer miles for an upgrade) then my company would permit me to fly in first class.
If you've flown both Alaska Airlines and Northwest in first class, then I'd highly appreciate it if you've could answer the following questions to help me decide whether or not I'll go first class on Alaska Airlines:

How does Alaska Airlines' first class compare to Northwest's first class?

If it's not compatible to Northwest's first class, then which airline's first class or business class does Alaska Airlines' first class compare to?

Is Alaska's first class better on their 737's or on their MD-80's (or is there no difference) ?

Thanks for your help!