Both are phenomenal.

If it were straight economy, I would say Asiana. Better pitch and probably better width as well.

EVA has the advantage over Asiana by offering Premium Economy on their transpacific routes for not a lot more cash than regular economy. EVA's premium economy is a lot like domestic first class on one of the legacy USA carriers. Premium economy is a gap in Asiana's product offering.

If it matters to you, Asiana seems to keep the cabin a couple degrees cooler.