I am helping a family member improve her credit card strategy so she can fly to Guangzhou (CAN) or Hong Kong (HKG). She flies China Southern a few times a year in economy. She's based out of Corvallis, Oregon, so the nearest large airport is Portland (PDX). She typically flies PDX-LAX-CAN.

What would be the best credit card to get to accumulate miles or points to redeem for these flights? I am guessing a Delta-branded card?