The Swordfish isn't entirely a paper aeroplane. It has some commonality with the SAAB Globaleye (sold to the UAE, in production), which has the same surface search radar & the airframe modifications for it, & perhaps some other shared modifications.
The Global 6000 is a pretty big business jet: about the same maximum take off weight as the Atlantique. Smaller & less power than the P-8, certainly, but not in the same class as the C-295 or ATR-72 MPAs.
I tried to find out what AESA is being used for the maritime surveillance radar on the Swordfish and Globaleye version with an increased maritime/ground focus but no luck as yet.
While I agree that the Global 6000 is in a different class from a C-295 or ATR72 MPA, the Bombardier Q400 MPA is not, and the Swordfish system is available on the Q400... That strongly suggests to me that the power budget for the Swordfish systems can be met by the Q400. On the good side, that would in turn suggest that the Global 6000 should have excess power generation available, leaving room for potential future development. However, the P-8A Poseidon also has excess power generation capacity so that there is some available for future developments. On the downside though, is that with the Q400 likely having a smaller power budget available and able to meet the demands from Swordfish systems, I would expect those systems to have less capability or performance.
One of Boeing's claims in it\s
P-8 Quick Facts (so take this with an unhealthily larger grain of salt) is...
P-8 has twice the sonobuoy processing capability and can carry 30 percent more sonobuoys than any maritime patrol and reconnaissance aircraft currently flying.
Having a greater processing capacity plus additional workstations would seem to give the P-8 an increased chance of detecting a contact if/when needed.
As a side note, the cost for a Globaleye in January was USD$236 mil. which was for a 3rd Globaleye for the UAE. While the Swordfish systems do not include the Erieye ER which the Globaleye has, the Swordfish system includes acoustic processors and ordinance/stores hardpoints and dropping capabilities. This would in turn suggest that while a Global 6000/Swordfish MPA might be less expensive than a Boeing P-8A Poseidon, if it was, it would probably not be substantially less. Meanwhile, it would almost certainly have a much smaller user base for future development.
