I am currently Gold with China Airlines (lowest tier) and am thinking if I should switch to Delta for FFP since now China Airlines is with Skyteam.

Travel mostly involve Transpacific between US, Taiwan, and China. About 3 to 4 times a year on the long haul and may be in Business and 6 to 8 times within East Asia. Occasionally random flights within the U.S. may be flown, but not much. Converting to miles would be at least 45,000 miles flown, average about 65,000 miles flown, and maybe 85,000 miles (counting the class bonuses if it's in Business).

Most if not all of these flights are on China Airlines (or DL codesharing it) so I am wondering if I should stick with China Airlines or move to Delta. The only thing I feel that's good staying with China Airlines is the award availabilities are better and I get lounge access already as Gold when flying CI.

If I try to make Emerald this year with it's discounts in qualifications, the only thing I feel DL may be better would be cheaper award miles, miles that never expire, and bonus miles. Is there another FFP option that's better than DL in this case?

- Lounge access is important
- Upgrades is somewhat important, but award tickets are okay as well

Any thoughts?