One thing Northern California and Sydney area shares are beaches. Both are cliffy with stunning scenic views. Surfers are out riding on waves and groups hang out on the sand. However, the similarities end there.
In the San Francisco Bay Area, where I am from, the water is cold all year long and swimming is usually avoided. Surfers often wear wetsuits to prevent hypothermia. However, the waters of Bondi beach were warm and excellent for swimming and no wetsuit is needed for surfers.
In addition, San Francisco Bay Area beaches are usually foggy or cloudy for much of the day and temperatures are mild even during the summer. But Sydney beaches are often warm in the summer. This makes it an excellent place to lay out on the sand and tan unlike the beaches back home.
However, one benefit of San Francisco Bay Area beaches is that many of them are not very crowded, especially the ones outside of San Francisco proper. It is easy to enjoy the stunning natural scenery in the San Francisco area without the interruptions of other people or having your photoshoot being photobombed.
Lastly, there is a lack of a boardwalk theme park culture in Sydney area. Bondi Beach had a small shopping strip near the beach, but the San Francisco area has the Santa Cruz boardwalk as part of the American beach boardwalk culture. The Santa Cruz boardwalk has many dining facilities, arcades, roller coasters, and other fun rides. This makes the beach much more than tanning, surfing, and swimming, but a place that have a variety of options for eating and playing.
Overall, coming from one coastal beach area to another, both the San Francisco Bay Area and Sydney have different strengths and cater to the different demands of the local culture.
Bondi Beach
Santa Cruz Beach Boardwalk (https://www.winecountry.com/businesses/11773/santa-cruz-beach-boardwalk)