Hi there!
As you hinted in your post, the Wild Animal Park has changed its name to the San Diego Zoo Safari Park, so if you're Googling for reviews, etc., try the new name.
I wasn't there for your trip 20 years ago, but I can say that certainly a lot has changed at the zoo in just the last few years, with millions and millions of dollars going into new, interactive exhibits. When you go during the hot months of summer, the animals tend to sleep during mid-afternoon, but you say you'll be going around Thanksgiving, so the temperatures will be better. There is a guided bus tour included with the general admission ticket as well as use of the Express Bus so that you don't have to walk quite so much. The Skyfari Tram is also included with a general admission ticket. They did JUST open (as in, last month) a 4D movie theater, but that costs a couple of dollars extra.
The Safari Park is a really cool park as well, but it doesn't have as much variety as the zoo. The Safari Park focuses on African and Asian animals, whereas the zoo has animals from all over the world. The main animals that are only at the zoo include the pandas, polar bears, orangutans, koalas, grizzly bears, kangaroos, sea lions (in the show), and many many more. I typically recommend that if you only have one day, do the zoo, but if you have two days, do both parks. Both parks are a lot of walking, so you can't really compare the two, plus at least the zoo has the transportation methods I mentioned above whereas the Safari Park just has the tram. Parking at the zoo is free while it is $10 per vehicle at the Safari Park.
Again, both are awesome parks, but if you only have one day, the "original", the zoo, is my recommendation.