I have a similar dilemma. The considerations:

- Current AA Gold and BD Silver, but not requalifying on either for 2006 due to excessive travel on SU (but not enough for SU status).
- MOW based, with most business travel to LON and long-haul travel to USA.
- Planned traveling to and within the US on DL and NW in the next 2 months.
- Historical accumulation of approximately 70,000+ miles on NW, 60,000+ on DL, 3,000 on CO (all either orphaned miles or non-flight earning, and pre-date SkyTeam and other reciprocity).
- Also have a significant number of UK-based Amex MR points, which can go to DL, CO, VS, BD (also AF, but at a poor rate).
- Short-haul traffic in Europe focuses on non-stops, meaning most frequently SU.
- I expect that I should be able to match to bottom-tier Elite status in the chosen program. DL only gives +25%, but NW and CO are +50%. All three give +100% for mid-tier.
- DL is currently the only one of the three serving MOW, though CO is expected to start EWR-DME next year. DL alone generally has better pricing to my key US destinations than connections on AF, etc.
- SU is reportedly to join SkyTeam in early 2006, which may necessitate a further re-assessment--either earn on DL/CO/NW for travel on SU, or switch all earnings to SU (likely to depend on various mileage-earning and redemption rules and other benefits that are specific to my travel patterns).
- AZ, AF and OK are of little appeal, as I see myself as unlikely to make significant numbers of flights on their respective metal.

Considering the above, NW and DL seem to be the best options, as I already have significant balances in both (I would prefer not to start accumulating in yet another program). From postings on FT I gather that CO is in many respects favorable to either, and the lack of transferability from Amex MR argues against NW. Does this mean that DL, which in general does not receive raving reviews on FT (and whose transatlantic product I abhor) is the best option?

What other recommendations does the general FT membership have?