The LA metro area is huge, I haven't lived in Orlando, only visited, so I can't exactly tell you how it compares, but here in LA (or SoCal for that matter) you'd have lots of options.
One of the best ways to determine what area you'd want to live in however, depends on where you'll be working & your daily activities.
In terms of theme parks, (with the exception of Universal which is in Hollywood / Studio City) Disneyland, Knotts, & Six Flags are about about 45 min - 1 hour away from downtown LA...(give or take depending on traffic)
But the outer "cities" & areas are cheaper, larger, & many have more amenities.
Here are a couple of areas.
The San Gabriel Valley: This is right outside LA & thee are tons of small cities here (Pasedana, Arcadia, Glendora, Azuza just to name a few.
Valencia / Santa Clarita: This is where Magic Mountain is, 7 you'll actually find a mix of expensive & affordable places here. It just depends on the building (many are new)
There's also plenty of areas south east of downtown, like Downey.
Walt Disney World's Magic Kingdom
Disney's Animal Kingdom
Disney's Hollywood Studios
Disney California Adventure
Universal's Islands of Adventure
Universal Studios Florida
Universal Studios Hollywood