Maybe the Qatar Q Suite is too new to be judged, but that's hands down the best J globally, even beating the DL one.

i've flown a variant of the DL seat sans the door in the form of SAS / SK. While it is nice, the new BE SuperDiamond used by AC AA CI and others are superior in terms of seat comfort, storage, and TV screen (which I've also sampled). I haven't tried 77W Polaris so I can't objectively comment on it.

And honestly, the LX 77W "throne" seat, which I'm flying very soon, offers far more personal space than the DL Suite.

So DL's uniqueness is really just that - a door.