Flecktarn, hands down.
We tested this in Sussex woodland back in the mid-noughties. I remember it like yesterday, big family get together from all over. The traditional DPM vs Flecktarn and a few of the non-military expensive brands. I've hunted with guys all over who swear by their brand's patterns. My cuzzies are rabid camo experts but they can't help it they're yanks. Kuiu, Realtree, Mossy Oak, Sitka, Hunter's Element, Stony Creek, blah blah blah. But the clever Germans worked it out years ago.
Put a person in a dark green trousers - not even camo trousers - and a Flecktarn shirt or jacket plus hat and neck gaiter, against the understory of typical English woodland, and the Flecktarn was the hardest to see when standing motionless. Easy winner. Happens to be the best in this part of the world too.