I think these two airports will always be in competition no matter what anyone says for one very good reason. In geographical terms the south side of Leeds might be LBA catchment, but in travelling time it's up for grabs. As a Leeds lad dragged up in Armley (not the jail!) who now lives 5 minutes driving time from DSA I know that it takes me about 45 minutes to visit the relatives in Leeds and then depending on the time half an hour to an hour to get to Yeadon. (Using the old name to prove I know what I'm talking about.) If you were talking to a travel agent and didn't like the sound of travelling to DSA, then the agent said 'well it might actually be quicker than LBA' it might make you more amenable, in spite of local loyalties.
Tim