They're genuinely different products, mate — not just different labels on the same tin.
Dulux Trade is the professional range, sold through decorators' merchants like Brewers and Dulux Decorator Centres. It's formulated for opacity and durability: more pigment, more binder, better flow. A Trade matt or the scrubbable Diamond Matt will cover in two coats where the retail equivalent often needs three to look right. That's why pros use it — fewer coats means less labour, and the finish wears far better in a hallway or busy kitchen.
Dulux retail — the tins in the big sheds and online — is aimed at occasional DIY. The colour palettes overlap but aren't identical, and the formulations are thinner. Once Upon a Time and the easycare ranges are perfectly serviceable for a quick bedroom refresh, but you'll fight the coverage on anything bold or over a colour change.
The price gap is smaller than people assume. Trade often works out cheaper per finished wall once you factor in the extra coat retail demands. If you're doing a whole room, go Trade every time.
Where I'd push you, though: if you're spending the effort to paint properly, Dulux isn't the only game. Little Greene Intelligent Matt and Crown Trade are both cracking for durability, and if you want depth of colour with a flatter, more characterful finish, Farrow & Ball Estate Emulsion or Earthborn Claypaint are a step up again. Earthborn's especially good in a nursery or older property that needs to breathe.
If you want a dependable Dulux-style result with a touch more soul, look at Dulux Heritage — it's their premium line with a richer colour book and a velvety finish.
Practical tip: buy Trade from a merchant, get them to tint it, and ask for the matching primer or undercoat for your substrate. That's how you get a flawless, long-lasting job — not just a cheap tin.