Where the thicker composite slab earns its premium, and where a good uPVC door is the right call.
The honest answer is that both are good doors used in the right place. Composite generally wins on front doors; uPVC often makes more sense on back, side and utility doors.
Here is the reasoning behind that.
A composite slab is thicker and denser, so it feels solid and resists flexing and warping. That matters most on a front door that is exposed, heavily used and the first thing visitors touch.
Both can be specified to a high security standard, and the lock cylinder and multipoint mechanism matter as much as the door leaf. The composite advantage is in resisting physical attack on the slab itself.
Composite offers deeper colours and more convincing woodgrain textures. uPVC costs less and is easier to justify on a rear door that nobody sees from the street.
We'll quote a composite and a uPVC option for the same opening and explain the difference in person.
Quality composite skins hold colour well, though very dark colours in full sun are always the hardest test for any door finish.
Not inherently — specification decides. A well-specified uPVC door with a good cylinder and multipoint lock is a secure door.
Composite slabs typically have a thicker insulating core, but the difference in a whole-house heat loss calculation is small compared with windows.