not really very tangible benefits...but here's the few major differences between Gold and Diamond that I see...

- access to F lounges when flying oneworld (Gold: J lounges only) with one guest (2 guests when flying CX and visiting a CX lounge)

- Diamond: access to CX J lounges even when not flying oneworld, with 2 guests

- 24 hrs guaranteed seat instead of 72 hrs for Gold, and valid for J/C bookings as well, not just economy (as for Gold)

- I believe they do have an unpublished "early re-qualification bonus" for Diamond's...i.e. if you re-qualify for Diamond early in your membership year, all your flight miles in the remainder of your current membership year earn you 100% bonus Asia Miles (an incentive to keep you flying even if you already have enough to re-qualify for Diamond)

- they are more willing to waive some service charges, e.g. "since you are a Diamond card member, we would waive the US$40 for changes in redemption group nominees"

- invitation to some Diamond/Invitation-members-only events ?