Its a difficult one, both airports have their merits and Belfast can sustain both managed correctly.
I do not buy into the need for a longer runway and i suspect they may not get it, what BFS needs is a high speed rail link from the city, BHD can handle most short haul stuff with the present runway, but could not hope to handle all of NI short haul requirements even with a longer runway.
I suspect Easy need to test the water, the increase in APD will make visiting to/from NI ever more expensive as you catch it both ways if flying to/from the main land and IMHO NI flights should be exempt from APD, you can hardly catch the bloody train can you? the ferry is a non starter for a day trip to watch MAN u or Liverpool
Not sure what Ryanairs beef about the runway is all about? who cares if you can only carry 150 just jack the price up to obtain the yield its the same for bmi or Easy