The Team DH is lighter than the A-Line. The DH is more oriented towards speed and handling while the A-Line is spec'd for bike parks, doing jumps, drops and various stunts. The DH can do all that just fine, just might not be as burly.
The Team DH is advertised as 40-41lbs out of the box, but really is about 42lbs; I can confirm this sometime this week. The A-Line will be about 1.5-2.5lbs heavier, I can't confirm this. The Team DH always has the most up to date frame while the A-Line's and other 8" freeride bikes use the previous year frame with minor updates. They both have the same travel, 7.9" and 9" of travel. They also both feature adjustable BB heights, 14.3" and 14.8" or so, check the Norco site for exact numbers.
Between the two frames, unless you are a top notch pro racer, you really won't notice the difference between the two. The biggest difference will be parts spec.
Since you are looking for a park bike, either will do just fine. Just pick the one with the parts spec that you like more and be happy.
I rented an A-Line while at Whistler along with some other bikes over the past two seasons. All bikes rode well, they all had minimal differences since I am not an experienced enough rider to take advantage of certain things, but I will say that personally the A-Line was one of the bikes that was a little more memorable (in a good way) than others. Because of this, I ordered a 2008 Team DH from my shop and hopefully will be giving it's maiden voyage at Whistler later this week.