There are many factors in a merger and what happens with each group. Both NWA and Delta have worries. The problem is that on a forum is when you post your concerns people on the other side take it as bashing their airline which in most cases is not the case. If you want reasons why most Delta pilots don't support the merger I will list some. I am not bashing NWA only putting down what the Delta concerns are. Some of those concerns are subjective and some are facts. Subjective is just that. Each sides will have a different opinion. Here is a short list of major concerns.

1. Seniority, In general the airline that has enjoy greater advancement can only lose in a merger.
2. Pilot Demographics, When you look at where the pilots on the combined lists actually reside it is obvious that there would be a seniority shift at bases. The shift in general would not go well for the Delta group.
3. DC-9's, They are not going to be here long term or even short term. NWA is retiring them at a rapid rate and the merger might accelerate that. There is the potential for a large job loss in particular if the replacement flying is at the connection carriers which I am sure is management first choice. (Note, the TA on the contract may have addressed this issue and could mitigate it)
4. Costs. NWA 10Q reports show their seat mile cost is above Deltas with the current pay rates for all employees at NWA. Bringing them up to Delta pay will increase that cost and lead to a large jump in the combined operations overall seat mile costs. Will it be a competitive airline?
5. Future advancement. Delta is bringing a large number of 777's to the property. They are staffed at more then 30 pilots per aircraft. There will be a lot of movement the next 3 years. A merged list would change the demographics of that movement.
6. Contract, Delta current contract has 21 months left to go. Openers will be exchanged soon. Some pilots feel we would do better to wait and go the traditional section 6 route at that point rather then agree to the 4 year deal offered in the merger. (Note, I disagree with this. I believe we would be better to take the deal now with the current economic situation and wait 4 years for the next contract.)
7. Internal strife at NWA between Redbook and Greenbook pilots. Most Delta guys were unaware of how much animosity there is between the groups at NWA. The contract and SLI negotiations surprised the Delta side. There were almost stunned by the level of hatred they saw and the issues it brought up. The observers or politico's as they were called hammered this home. It could make having a unified pilot group for future contracts difficult.

There are other points but I think these are the main issues. Again I am not bashing NWA. I am sure that NWA pilots have as many or more concerns on their side also. The real point is that given those concerns on both sides perhaps the proper course of action is for both MEC's to come out in opposition to this merger now. Contrary to some posts we do have a lot of clout and can impact if this merger occurrs or not. I think the Delta scope provisions alone could be a deal killer. One last point. Both airlines also bring a lot of positives to a merger. The question was asked why Delta pilots opposed the merger and I answered. I could post a large number of reasons why the merger might be good that NWA brings to the table. At the moment however the overall balance leads me and most Delta pilots to favor the go it alone strategy.