These two get pitted against each other a lot, and honestly both are good. The question is what you're paying for.
Little Greene is the proper heritage brand of the two. 251 colours, with a genuinely deep green range (48 of them) and a wide LRV span from 0.4 right up to 98 — so you've got everything from near-black to the cleanest off-whites. The pigment load is generous, the colours have real depth and shift beautifully through the day, and the finishes (Intelligent Matt, Absolute Matt) are lovely to live with. Greens like Mister David and blues like Air Force Blue show off exactly what the brand does well — colours with body and character rather than flat, one-note tones.
Dulux Heritage is the smart-money option. 112 colours, weighted towards neutrals (27) and whites (26), with a tighter LRV range of 3.7–86. The palette is more conservative — it's built for classic period schemes rather than statement walls. Indian White is a cracking warm off-white for a whole house, and Panel White is a clean, crisp trim white that works against almost anything. The paint covers well, the matt is a proper flat finish, and it's mixed through the Dulux network so it's easy to get hold of and re-order.
The honest verdict: if you're doing a deep, characterful colour — a green snug, a moody hallway — spend the extra on Little Greene. The depth genuinely shows. If you're doing neutrals and whites across a family home and want to keep the budget sensible, Dulux Heritage will not let you down and you'll barely notice the difference on a pale wall.
Practical tip — don't mix and match brand whites on the same job. Pick one brand's white for all your trim and stick to it, or the slight undertone differences will nag at you in daylight.