QR is probably the best bet. Their B777, which I believe they use both to EZE and PEK (at least today), is 2-2-2 across, fully flat, and pretty comfortable as you say. I don't think that anyone would be better on this route.

Another option is TK. If you can get their 777, it's comparable to QR; 2-3-2 across, though with the same seat width according to seatguru. Worth checking the price.