I'd definitely recommend the Korean Air option. As a general rule, Mainland Chinese carriers are not the most appealing airlines to take (apart from a few examples like Xiamen Air and Hainan Airlines, among others). On many flights, there's the hassle of not being allowed to use your phone even on airplane mode.

To add to that, if you could choose the KE flight from San Fransisco operated by the 747-8i (usually KE24), you'd be treated with direct aisle access from all seats as these flights feature a "suite" configuration as opposed to the traditional forward facing seats on some other Korean Air planes. In that case, I'd personally be inclined to take a window seat as it offers the most privacy.