I have heard the following:
-) Thanks to the revised contracts (-37%!), the DAT Avro's cost only about half as much as the VEX B737s.
-) Unlike the owners of DAT's Avro fleet, the leasing companies owning the VEX B737s do not want to reduce their leasing terms substancially as they think current market value of a B737 has not reduced that much. (I believe the maximum offered was -10%)
-) Right now DAT can lease some of the ex-Sabena A319s for 30% less then the average VEX B737!
-) The Sabena A319s are brandnew, whereas the VEX B737s are older and more used.
-) The Sabena A319s are more comfortable then the B737-300/-400 and unlike the VEX B737-300/-400 they have the much needed full business class configuration (seats can be configured to a 2/2, 2/3 or 3/3 seating configuration).
-) The A319 consumes less fuel then the B737.
-) DAT plans to fly to Africa and needs long haul planes for that. In a first phase they will probably start with 2 wetleased B767s, but if the aim is to have an independant operation, then the A330 is the preferred plane (for almost the same reasons the A319 is preferred to the B737). Note that there is cross qualification possible on A319/A330, something not possible with B737/A330 or B737/B767. Cross qualification on A319/A330 has also been formally introduced in the new DAT labour agreements.
In short, I think that a merger between the companies might also include a change of plane...