Which cities in the US would you be visiting (from ICN or PEK) and how often? Do you already know which airlines (US based or Asia based carriers) you are considering to fly with in 2010? Basically you want figure out what are the non-stop routes (if possible) across the pacific then determine the trade off between different options.

You stated below that you are most interested in free upgrades -- are you talking about upgrades for flights within the US or the long haul transpacific flights or potentially flights within Asia? For US domestic travel, as a mid-tier elite, you can have a varying degree of likelihood of free upgrade depending on the routes and timing (i.e., # of other elites who'd be traveling).

As a mid tier elite, you typically don't get "free" upgrade for long haul transpacific flights. Some airlines (e.g., UA) have instruments for upgrades for TPAC travel however only those with a higher elite status (100K+ EQM) are given the SWU and also there might be a fare class requirement for upgrades -- check the specific airline website for instrument based upgrade requirements for TPAC flights. Another *A airline, CO, does not have free upgrade for TPAC, but you can use "miles + cash co-pay" to upgrade any coach tickets.

One of the main benefit for reaching mid tier elite status is that you typically get 100% bonus miles (redeemable miles) of the actual miles flown. While you're choosing a FFP, consider how you'd want use the miles and whether the FFP would be a good fit for your redemption needs.

Lastly, not forget that one of the good things about UA is that it has E+, so if you are tall that would be a big factor in favor of UA for traveling in coach.

Best of luck.