These two aren't really rivals — they're different beasts.
Dulux is the giant: 2,092 colours, strongest in Neutrals (335), Blues (265), Greens (262) and Whites (201), with an LRV range of 1.2 to 92.3. You can colour-match almost anything, mix it at any merchant, and there's a Dulux product for every job — emulsion, trim, masonry, the lot. If you want a deep, dramatic colour, Dulux has the depth to do it — something like Night Jewels 1 for a moody bedroom, or the warm metallic glow of Pharaohs Gold 2 for a feature wall. Availability and tinting flexibility are unbeatable.
Lick is the opposite philosophy: just 99 colours, deliberately edited so you don't drown in choice. Greens (19), Neutrals (13), Blues (13) and Whites (12) lead the range, with LRVs from 3.3 to 100. The whites are genuinely good and easy to live with — White 07 is a soft, warm everyday white, and White 01 is your cleaner, brighter option. It's app-and-online led, sample-swatch friendly, and the formulation is low-VOC and pleasant to roll. The trade-off is you can't pop to the merchant for a tin, and the palette won't suit you if you want something obscure.
The honest "but what about quality" answer: both are perfectly good modern emulsions. Lick's matt has a nice flat, contemporary finish; Dulux Diamond Matt is the more wipeable, hard-wearing choice for hallways and kids' rooms.
My advice — if you already know your colour and want it on the wall this weekend, Dulux wins on convenience. If you're starting from scratch and want a curated, fail-safe palette delivered to your door, Lick makes the decision easier. And don't overlook the rest of FiniSpec's range: if you fall between the two, brands like Earthborn or COAT often hit that sweet spot of curated-but-characterful.