Hi Ho Hun. he way I understand it, old J2M was otw to the scrap heap in favor of the N1K1/2J. However as I understand it... once the B-29 started showing up over Japan... things changed. Raiden was given a second look and a new lease on life because I could climb like the devil.
According to Francillion (who isnt always correct, but good enough for an overview)
N1K2-J:
Max Speed - 369 mph @ 18,375 ft
Time to 6000m - 7m-22sec (7m-50sec for N1K1-J)
Wingloading N1K1J - 34 lb sq ft
Wingloading N1K2J - 34.9 lb sq ft
Powerloading (both) - 4.4 lb/hp
J2M3:
Max Speed - 365 mph @ 17,390 ft (J2M2 371mph @ 17,880 ft)
Time to 6000m - 6m-14sec (J2M2 5m-38sec)
Wingloading J2M2 - 32 lb sq ft
Wingloading J2M3 - 35.1 lb sq ft
Powerloading J2M2 - 3.9 lb/hp
Powerloading J2M3 - 4.2 lb/hp
The N1K1/2J also had about 50% MORE range than the Raiden. Not big news in a game, but critical for real pilots in a real war.
So, it seems like the are both rather similar, with the J2M3 being more of a sprinter or Hotrod. Yes two cannons on the raiden were Type 99 1 (worse than MG/FF in raw data), but hell, it fired the same shell as the Type 99 2.
The Raiden would be an awesome in game point defense intercpter compared to the N1K. Basically, its a trade of, Climb vs Range.