Here's my thoughts. And, they probably don't apply to most people planning trips. But, anyway...
I, too, will be making my first trip to DL next weekend. I have been to WDW somewhere around 150 times. I will be with my 7 year old daughter (who has been to WDW around 60 times). Our first park day will be Friday, and we will be visiting
Disneyland. Disneyland is about 97% of the reason we are going.
I'm one of those people who believes in the importance of "firsts." When we first took our daughter to WDW when she was 1, I wanted her first theme park, and first attraction to be particulary special and have some meaning. So, clearly, The Magic Kingdom was the choice of first park. But, the choice of attraction required more thought. I wanted it to be an attraction that Walt had a great deal of influence on (even if it wasn't at his original park), one that was part of the common vernacular, one that was really age appropriate for a little kid, and one that would likely be around for quite some time - so that she could ride it over and over as she got older. The choice was "it's a small world."
So, as I approach our first ever trip to Disneyland, the importance of "firsts" is just as strong. My thought process is this - Again, I want our first Disneyland attraction to be one that had a great deal of influence from Walt (preferably opening during his lifetime) and one that has chiseled itself into our culture. Plus, I want it to be an attraction that (while possibly the same in name and concept) differs enough to make it unique from WDW.
With a great deal of thought, I've decided that Pirates of the Caribbean will be our first Disneyland attraction.