Eh, I disagree. While the Safari Park is an excellent zoo, among my top 5 favorites, it isn't in the same league as the San Diego Zoo in my opinion. The one area that the Safari Park is clearly better than the Zoo is for large mammals (then again, the Safari Park is one of the best in the world in this regard), but in every other area the zoo is clearly superior both in collection and exhibitry. The Safari Park has a small, but interesting bird collection in mostly good habitats, but it isn't even on the same level as the zoo, ditto for smaller mammals, and it's almost non-existent reptile collection pales in comparison to the zoo, which is arguably the best in the world for Reptiles and Amphibians. If I could re-visit one of these two zoos today I'd pick the San Diego zoo in a heartbeat, the Safari Park is great but the Zoo is just better. Just my two cents

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I see where you are coming from, but in my opinion the Safari Park is undoubtedly the better of the two. If I were to re-visit one of them, it would be the Safari Park a million times over.
First, I believe in assessing zoos and aquariums based on what they are trying to be and not on what they are not trying to be. The Safari Park is not trying to beat the zoo in terms of its collections of reptiles, amphibians, birds, and small/medium-sized mammals. However, I absolutely think the Safari Park is better at its strengths than the Zoo is.
I also am a quality-over-quality person, and I would rather see a smaller amount of species in fantastic habitats over more species packed in a smaller amount of space. And in my opinion, the habitats at SDWAP for its less speciose but larger body-sized collection are more impressive and enjoyable and memorable than the Zoo's habitats. I'd rather see the large field habitats for many species over the large animal habitats at the zoo. I'd rather see the Wild Animal Park's tiger habitat over the (recently split, from what I have heard) Tiger River, and ditto to the SDSP's elephant and lion habitats over what they have in Elephant Odyssey. The new Australia zone looks better than the Zoo's Outback does. Even some of the aviaries and indoor habitats at the SDSP were better than often given credit imho.
And that's the thing. To me, San Diego Safari Park was the far more memorable experience of the two. Even including things beyond the zoo nerd's usual preferences. For instance, I enjoyed the Petting Kraal at SDSP, with its mixture of domestic and exotic ungulates, much more than the Zoo's Children's Zoo.
On that last point, I will say that I do think the Sanford Children's Zoo and surrounding area planned at SDZ easily looks like the best children's zoo I have ever seen with different habitat zones for many smaller species, Komodo dragons, a new hummingbird aviary, another aviary, a reptile/amphibian/fish house, insects, beehive, etc. I would have to see what it looks like as a final product of course, but the plans to me look fantastic and infinitely more interesting than more barnyard contact zones.
I am not saying I dislike the Zoo. I do think it's a fantastic zoo, but it's not the best zoo either in my opinion. And I say that as someone, who, for all purposes should be biased toward it over the Safari Park, because I am much more into birds, reptiles, and amphibians than I am into mammals. There's nothing wrong with having different preferences either, but that's what zoo opinions are based on in the end: personal preferences.