Coolfish, I'm in virtually the same boat as you and struggle with the same dilemma. Even my travel pattern is similar: 3~4x per year TPAC, plus undeterminable amount of intra-Asia trips. Main difference is that I don't get to fly paid business class.

I used to do all my long-haul travel on CI, but since CI joined ST, I'm opening up my routings to ST partners... but still contemplating what FFP to pool miles in. However, the only viable alternative to me is DL, which is the sole US-based SkyTeam FFP. (The only other ST FFP I'd consider is CZ.) Here's my take on your (and my) situation:

Status
I imagine the goal is to have ST+ Elite status so you can get lounge and other benefits throughout the alliance. ST+ is achieved at CI Emerald, which, with your travel pattern, will be difficult to maintain (110k). The current promo brings down the qualification to 70k miles, which helps, but is still more than the 50k needed for DL Gold. Under such circumstances: only prioritizing achieving status and given the current CI promo, if you need <50k miles to achieve CI Emerald (and can complete this by 2012/9/30), then it may make sense to go with CI. Otherwise, it may even make sense to start fresh and pool miles with DL.

Award Redemption
Travel between US-Taiwan/China = US-North Asia redemption. As you mentioned, DL has cheaper award redemptions: non-CI ST partner Y-class R/T costs DL 70k or CI 110k... even a redeeming on CI with CI miles will cost 100k. DL seems more advantageous here.

All in all, I personally am leaning toward pooling with DL:

• I will not be able to hit CI Emerald even with the current promo; furthermore, I will never be able to maintain CI Emerald's 110k renewal requirement. Hence, I might as well give up going for ST+ and just go for DL's easier-to-achieve-than-CI Gold FO tier.
• With status out of the picture, my goal is more in line with an earn-and-burn setup. With DL's award redemption being substantially cheaper, it only makes sense to pool with DL.
• DL is a AMEX MR transfer partner, which is a huge miles-generating avenue.

Suggestion:
Since you mentioned that lounge access is important, have you considered getting the AMEX Platinum card? You get the MR-SkyMiles transfer route plus Priority Pass. While PP may not be the same as having ST+, I believe it covers more airports overall.