This has been discussed several times. You will get plenty of automatic responses in favor of KE., but I would generally lean DL unless the price difference matters.

First and foremost is the equipment. Last I flew KE I was still up front in 2-2-2, not 1-2-1. And if they are still flying the A380 on the route, once was enough for me.

I do give KE a win on dinner, though try to get your order for bim-bop-be (or whatever it is called) in early if you want it.

With KE you will certainly get plenty of happy smiles , "Mr"s and "thank you"s. But at the end of the day I found DL service just as good or better at actually getting me food and drinks.

My final answer would be based on the seats if KE is 2-2-2. And schedule if not. Again, weighed by price of course.

EDIT: No post COVID experience for me.

EDIT2: If things ever get back to the old world order, CI (cheap mile awards) and MU (cheap paid C) were both solid options wih modern C seats. Both have modest service issues compared to DL/KE, but the savings was huge. Be careful about CI now as the transfer is price scam (and MU is of course out of the question).