Simply White is one of Benjamin Moore's best-loved off-whites — a soft, warm white with the faintest yellow undertone that reads clean without going clinical. But BM isn't cheap, and you don't need to pay the premium to get that look.
Dulux New Meringue is your best bet. At LRV 83.8 it's bright and airy, and it measures ΔE 0.8 from Simply White — that's imperceptible to the eye, the kind of gap you'd never spot on a wall. You'll get it trade-priced through any Dulux Decorator Centre, and the Diamond Matt or Vinyl Matt finishes wipe down well in living spaces.
If you can source it, Crown Collector's White is technically the tightest match at ΔE 0.7, LRV 86.9. It's a touch brighter and cleaner, so it'll bounce a little more light — handy in a darker room. Crown's quality is solid and the price is keen.
The third option is COAT Pampas at ΔE 2 — still a very close match, just a hair softer and creamier (LRV 78.8). COAT isn't dirt-cheap, but it's water-based, low-VOC, and delivered to your door, so it's worth a look if you'd rather skip the trade counter run.
The usual caveat: a colour match gets you the same hue, but not necessarily the same paint. Benjamin Moore's Regal Select and Aura have a particular depth and coverage that's part of what you're paying for. A ΔE under 1 means the colour is bang on — the finish, opacity and durability come down to which product line you pick. For a warm off-white like this, two coats of Dulux Diamond Matt over a decent primer will look every bit as good on the wall.
My advice: grab a New Meringue tester, paint a big patch next to your trim, and check it morning and evening before you commit. Warm whites shift with the light, and that's the bit no ΔE figure can tell you.