If you are only doing one, do the zoo.
The Wild Animal Park has many large animals in an huge, open enclosure, so giraffes mingle with ostriches and such, in addition to several smaller single-animal enclosures. It is in a very scenic, rural area, and covers a lot of acreage. The views are breathtaking, and there are some extremely rare animals there, like the most endangered rhinoceros in the world. They also have a very successful breeding program, and currently have baby giraffes, elephants, etc.
The WAP is a San Diego Zoo park, and the two share a website at sandiegozoo.org.