These two come at colour from different directions, and that's the whole decision.
Little Greene is, first and foremost, a paint maker. The card runs to 251 colours and the strength is greens — 48 of them — followed by 44 neutrals, 28 blues and 22 whites. That green range is genuinely one of the best in the business, and the LRV spread runs the full gamut from 0.4 right up to a near-pure 98, so you can go pitch-dark or properly bright. The paint itself has lovely depth and the finishes are robust. Air Force Blue is a cracking example — a confident, smoky mid-blue that holds its own in north and south light. Mister David shows off the warmer, more characterful end of their neutrals.
Sanderson is a furnishings house at heart, and its 154 paint colours exist to coordinate with its fabrics and wallpapers. The palette leans into neutrals (27), greys (22), whites (22) and blues (21), with an LRV range of 3.6 to 89.7. If you've fallen for a Sanderson print and want walls that sit beside it perfectly, that's exactly what this range is built for. Airlane Blue and Amanpuri Red are good illustrations — colours designed to live within a scheme rather than shout on their own.
So the honest steer: if you're choosing paint led by colour and want range and depth, Little Greene wins on breadth alone — and the green selection seals it. If you're choosing paint led by a wallpaper or fabric you've already committed to, Sanderson is the smarter call because the coordination is baked in.
Practical advice: don't decide off the card. Order sample pots of two or three from each and paint a large patch — A2 minimum — on a bit of board you can move around the room at different times of day. Colour shifts more with your light than it does between brands.