Almost every buyer looking seriously at the top of the Dallas market considers both. They are the two most established addresses in the city and they are not versions of the same thing — they answer different questions, and the honest answer usually comes from which question you are actually asking.
The structural difference
Highland Park is a town. An independent municipality with its own government, police and public works, entirely surrounded by Dallas, served by the Highland Park Independent School District. It is small, fully built and cannot expand.
Preston Hollow is a Dallas neighborhood. It is part of the City of Dallas, considerably larger, and defined by land rather than by governance.
Nearly every other difference follows from those two facts.
Land
This is the clearest divide. Preston Hollow lots of one to three acres are ordinary, and larger parcels exist in the older core west of Preston Road. Highland Park lots are generally smaller and far more uniform, because the town was planned at a walkable density.
The consequence is that in Preston Hollow the land frequently leads the value and the house is what currently sits on it. In Highland Park, where you cannot buy more land, the pressure falls on the house — its condition, its renovation history, its position on the block.
Architecture
Preston Hollow has no prevailing style. Georgian and French traditional houses sit beside significant modern and architect-designed work and continuing new construction. A large, flat, screened parcel imposes very little, so the neighborhood is a record of what successive owners wanted.
Highland Park is predominantly period: Tudor, Spanish Eclectic, Georgian, Colonial Revival and Mediterranean, largely 1910s to 1940s. There is contemporary work and some of it is very good, but the prevailing grammar is traditional. A buyer whose priority is modern architecture will find more of it in Preston Hollow — or in Bluffview.
Privacy versus walkability
Preston Hollow is arranged around not being seen: deep setbacks, gated motor courts, dense perimeter planting, long drives. It is not walkable in any meaningful sense, and that is the point.
Highland Park is the opposite trade. Houses sit closer to the street on a consistent, maintained streetscape, and the town is walkable to the parks, to Turtle Creek and to Highland Park Village. You are more visible and more connected.
Schools
Highland Park is served by the Highland Park Independent School District, and for many buyers that is the decisive fact. Preston Hollow is served by Dallas ISD, with several private schools within the neighborhood itself. Buyers weigh this differently depending on whether they intend to use public or private schooling, and it is worth being explicit about which before comparing anything else.
Inventory and how it moves
Both are tightly held, and both have a meaningful private market. In Highland Park it is a function of a small town where owners of notable houses prefer discretion. In Preston Hollow it is a function of estate owners who do not wish their property cataloged.
In either case, a buyer relying only on published inventory is seeing part of the picture. How that market works.
So which one
Preston Hollow if you want land, privacy and architectural freedom — particularly if you may build, rebuild or substantially alter, or if you want a modern or architect-designed house.
Highland Park if you want the school district, walkability, a consistent streetscape and an address whose desirability has proven stable across a very long period — and if you are content to work within an existing house rather than reshape a site.
In practice a great many buyers look at both and let the individual house decide, which is a perfectly sound way to run a search provided you know what you are trading in each direction. Alex Prado advises buyers and sellers in both, typically across the $2M to $10M-plus range.