Other than being stunning in photos and in real life. For me it's the technology that was used on the aircraft. The engineering and design of the P-61 to me is amazing. From the radar system, semi automated turret, night vision ability, wing and control surface designs, the shear size of the 61 being the largest US fighter, and mostly the history of the 61 and their crews.
As for in AH, it is a plane that I think would be used by many, not only an attacker but also a fighter as well. With its range, weaponry, and potiental maneuverablity. (I say potential as I have never flown a 61 to make a true judgement)
I don't think the 61 will be such an über ride in the MA, comparatively speaking the 61 is massive compared to say a 47 or 38.
How do you mean the better of the two Sir? Are you referring to the production numbers or WWII intended design as a "night fighter"?