JMSDF spanks the USN

Well, spanks the P-3 bubbas at least. Have you heard about the "XP-1?"

Nice stats.
Kawasaki Heavy Industries (KHI) P-X — Specification

General characteristics

• Crew: Flight:2 Mission:(N/A)
• Length: 38 m (124 ft 8 in)
• Wingspan: 35 m (114 ft 8 in)
• Height: 12 m (39 ft 4 in)
• Powerplant: 4× IHI F7-10 ^[7], 13,500 lbs (60 kN) each

Performance

• Cruise speed: 833 km/h (450 knots, 516 mph)
• Range: 8,000 km (4,320 nm, 4,970 mi)
• Service ceiling: 44,200 ft (13,520 m)

Armament

• Bombs: 20,000+ lb (9,000+ kg)
• Missiles: AGM-84 Harpoon, ASM-1C, AGM-65 Maverick
• Sonobuoys: 30+ Pre-loaded, 70+ Deployable from inside
• Other: MK-46 and Type 97 and new(GRX-5) torpedoes, mines, depth charges

Avionics

• Radar Toshiba Active Electronically Scanned Array radar system
• Sound NEC Multistatic sound navigation system
• ASW SHINKO ELECTRIC CO.,LTD. Advanced combat direction system
• Other Mitsubishi Electric Countermeasure system (CMD,RWR,MWS,ESM)

• 
  

Four engines are nice. Let's compare to the P-8A estimate...
Boeing P-8A Poseidon (MMA Project ) — Specifications

US Navy Fact File - P-8A ^[9] and Boeing P-8A Specifications ^[10]

General characteristics

• Crew: Flight:2 Mission:7
• Length: 129 ft 6 in (39.47 m)
• Wingspan: 117 ft 2 in (35.72 m)
• Height: 42 ft 1 in (12.83 m)
• Empty weight: 138,300 lb (62,730 kg)
• Max takeoff weight: 188,200 lb (85,370 kg)
• Powerplant: 2× CFM International CFM56-7B, 27,000 lbf (120 kN) each

Performance

• Maximum speed: 490 kts (907 km/h)
• Cruise speed: 440 kts (815 km/h)
• Service ceiling: 41,000 ft (12,500 m)

Armament

Joint missiles, Mines and Torpedoes

Avionics

Raytheon APY-10 (APS-137 follow-on) surface search radar and SIGINT package.

Less data for the P-8A, must be because there is yet to be one making a shadow on the ramp - which is a shame being that we know how the P-3s are doing.

There are some interesting quotes to take on board.

[1] In this the P-X program will be the exact reverse of the P-8A. The latter is a maritime patrol derivative of Boeing’s highly-successful 737 airliner. KHI, in contrast, built a patrol aircraft but may offset development costs by spinning off a future YP-X civilian airliner derivative. Update: The Japanese Ministry of Defence’s Technical Research and Development Institute site refers to the P-X prototype as a “XP-1”.
[2] One batch of rivets from a US supplier had not been heat treated. As a result, 10,000 rivets in 161 locations had to be examined. Many of the rivets had to be drilled out and replaced.

Here too.

In contrast with the case of ballistic missile programs – in which Japanese generally expressed a desire to be a partner with the United States – development of an indigenous P-3 replacement was characterized as having been decided officially, with consideration being given to maintaining interoperability with US systems. Japanese believed that the United States had lagged behind Japan in articulating requirements for a P-3 replacement, leading Japan to initiate its own programs independently.

...and it flies!