My husband is Diamond on CX and I was looking at fares for HKG-NRT round trip economy. JAL pricing cheaper on CX flights (codeshare but operated by CX). Any downside to booking with JAL besides less mileage? I called AM rep and they said we would still be able to get baggage and lounge access benefits.

Website not much help.

"Note: The above-mentioned benefits are available only to members departing on flights marketed and operated by Cathay Pacific/Dragonair, and do not apply to joint operating or codeshare flights operated by third-party carriers."

In this case it would be marketed by JAL and CX (and I would buy via JAL) but operated by CX.

Anyone been in a similar situation and can let me know any other downsides?