Airframe or Mission Systems
It seems all the arguments here are about which airframe is better suited to the MPA or MMA role.
The 'old and bolds' argue that the P8 is ill suited to operating at low level and will not meet the range or endurance that the P3 or Nimrod are capable of.
So far I have not seen anything to indicate this; by all reports it is meeting or exceeding it's directed capability in those areas.
The argument that P8 is the wrong airframe for the job because it is not yet fully mission capable is flawed. The mission systems are having problems, apparently due to software issues, but these can by rectified by updates. How did the latest P3 or Nimrod upgrades go at first? Australia and the UK would receive Increment 2 or 3 aircraft based on how far away delivery times are.
An 80% mission capable P8 which can get airborne. is still better than a fatigued and unserviceable P3 or Nimrod.