In our specific circumstance, it seems like it shouldn't matter whether the SLI is weighted towards Relative Seniority or DOH because whether a 10 year VX guy is placed next to a 20 year AS guy on the Master List or, all the VX guys are placed near the bottom of that list, in practice because we are currently in different bases and fly different types, each pilot typically won't "lose out" to a guy from the "other side".
The philosophical argument should favor Relative Seniority over DOH however, because the more senior you are on your respective list, the higher the possibility (and your expectations) of you ending up retiring closer to the top of that (your original) seniority list. By placing virtually all of VX pilots close to the bottom of a combined list, that possibility of enjoying some level of a really high seniority at some point in your career would be seriously eroded.
If you go with Relative Seniority however(with some weighting for longevity of course), yes a 10 year guy at AS who was expecting to upgrade in 3 years might end up getting slotted beside a 6 year VX guy who was also expecting to upgrade in about the same time, but on this combined list, they both would probably now end up upgrading in that similar time frame...... in line with their original expectations
Consequently, both of them would still have a reasonably fair shot of ending up super senior at some point in their future career.
That in my opinion is more equitable.
(I will readily admit that I just pulled these numbers in the example out of my *ss, so if there are any statistically gifted pilots who can run the numbers for both scenarios and give us a breakdown, it might be interesting to see
In a perfect world there would be no mergers, and we would happily move up our own seniority list until one day we are at the top of the hill sitting pretty. But mergers are a reality and invariably some pilots will end up at a disadvantage relative to others after an SLI exercise. The trick is to complete one, so that the least amount of the pilots end up getting the shaft.