Should I start with Angry Birds or Angry Birds Seasons?

There are two versions of Angry Birds on the app store: The original, and an "expandalone" with a couple sets of seasonal levels (Halloween and Christmas, currently).

I haven't played either one. Does the expandalone's level design assume a familiarity with the original game? Which one should I play first?

I would suggest starting with the original Angry Birds, simply because it contains much more levels than the Seasons edition. (The original Angry Birds has 11 worlds as of this post, and the Seasons edition has 3 Halloween worlds and 25 Christmas levels.)

The Seasons edition is more of an extension to the original.