Personally I prefer DL based on the seats.

The service issue is a wash for me. The Asian airlines in general will do a better job of smiling and saying please/thanks about a hundred times a flight. But they refuse to grasp that some drink more than 6 oz of whatever an hour.

It is a smallish difference, and my next award flight is on KE to save miles. I would not spend more for a DL award (nor the other way around).

BTW: You likely get in to BKK a little earlier flying KE. Not a totally irrelevant issue as you try to adjust.