Orlando, Hollywood, or both
They are not the same trip and people conflate them constantly.
Universal Orlando is a multi-day destination. Multiple parks, on-site hotels, and now Epic Universe, which changes how many days you need. Three days is tight. Four or five is comfortable.
Universal Hollywood is a single park and a day trip. It works beautifully bolted onto a California holiday and badly as a destination on its own.
If somebody has told you a Hollywood trip is equivalent to Orlando, they have not been to both.
Express Pass, and when it is worth the money
This is the question that decides your day, and the answer is genuinely conditional.
At Universal Orlando, Express Pass is included with the top on-site hotels. That single fact often makes an expensive hotel the cheaper option once you price the passes separately for a family. Doing that arithmetic properly is most of the value I add on a Universal trip.
In quieter weeks you may not need it at all. In peak weeks it is close to essential. I will tell you which one you are looking at.
SeaWorld, and why it belongs in the conversation
SeaWorld gets left out of most Orlando planning and it should not be.
It is a genuinely good park, the crowds are lighter than at the big two, and the multi-park tickets that bundle it with Aquatica and Busch Gardens are among the better value in Orlando. For families with younger children, or anyone wanting a slower day in the middle of a fast week, it does a job the other parks cannot.
I book SeaWorld both on its own and as part of a wider Orlando trip, and the ticket combinations change often enough to be worth asking about rather than guessing.
What catches people out
Epic Universe has changed the maths. The day counts that worked before it opened no longer hold.
On-site is not one thing. The hotel tiers differ enormously, and only some of them include Express Pass. Booking the wrong tier to save money can cost more once you buy the passes.
Park-to-park versus single park. If you want to ride the Hogwarts Express you need park-to-park, and people discover this at the gate.
Heat. Orlando in July is brutal and a midday break at the hotel is not a wasted afternoon, it is what makes the evening possible.