I am not a Mosquito fan, particularly. As a kid I had an unnatural affection for the P-61. Nor am I British. But this seems like an easy call: Mosquito.
It had the best or tied (US derivatives of GB sets) with the best radar. Esp important in comparing vs GE ac as Mossie (over GE/occupied) operated with no/little/or longrange (read:weak) GCI for most of the European war. Put any of the Allied ac with a MK X against any of the GE over neutral non-GCI airspace and it would generally be a very lopsided fight.
Two man crew (required) seated side-by-side (true of only a few and very underestimated in it's importance).
Range (and lets give credit for having to haul the fuel load to take the fight TO the enemy and return..) to fly/fight in excess of the mission requirement.
4 reliable, tightly grouped, high-rate 20mm mounted low (flash) and lugging large (bombay) ammo hoppers surely was sufficient to the task and generally exceeded the various and dubious fitments experimented with elsewhere.
Speed. It is possible to quote some stat on some ac from somewhere on one special day, but the settled truth is that unless it was a jet or a late-war single seater starting from just the right position and energy-state, the Mossie was going to leave you talking to yourself..... unless it was chasing you.. Important connection to range here... Mossies in threat areas had the option (taken unless offset by a tactical consideration) to "cruise" well up in the bit. Ac do not instantly accelerate. Nor, as long as we are on speed, decelerate instantly. Which is a good place to bring up the 262. Given the need (less for the GE, true) to ID aircraft and the tremendous difficulty (applies to everyone) in estimating range at night (the danger of collision was tremendous), there is definitely such a thing as too much closing speed. Paired with this then is the benefit of being able to shed speed quickly (without maneuver if possible or risk losing contact or being detected). The Mossie had no special talent here (unless the other aircraft was much heavier) over other propeller ac, but was a real liability for 262. It's alternative was to fire from possibly too far out (alerting the target) or waiting (closing fast) until the sight picture firmed up at which time it possiblly collided or, more likely, got off a snap shot before having to turn off. From what I have read, the only real advantage of the short range but very fast 262 as a NF was that it offered great protection from the greatest (at least most feared) danger to a GE NF pilot: Mossie. Score Mossie.
Agility: Daytime Mossie vs 110 fights went mostly Mossie re agility. With that poss exception out to the way, Mossie was at least as agile as any GE twin. As to other allied... if so, they didn't demonstrate it in combat. The P-38 had similar performance numbers, but it didn't actually serve as a NF, so drop that. Please. And, just like the 262's difficulty in using big speed while on the offense, there is a limit to how much agility is useful at night. Given the difficulty in retaining a sight picture combined with the very real possibility of vertigo, then past some desired agility capability comes the likelihood that it comes at the cost of being a friendly IFR platform.
So, Mossie: you cant catch it; or you can't get away. If there were no GCI and you are a GE, you are very out radared. Unless you are in a 262 and run away...that is unless you have land soon (and you do) and Mossie follows. If you engage (still flying a 262) and he knows you are there (and he probably does, better radar), then you need to get lucky in a fast pass because Mossie is absolutely more agile than a 262 (demonstrated many times in combat by photo-recon Mossies).
Getting back to the question: Best night fighter. Just like daytime; what is the mission? Interception over home turf? Did that, though by the time Mossie was on strength, not a lot of targets over GB. Long-range night harassment of enemy airfields and night bombers in the pattern? GE did a little, but Mossie wrote the book. Pro-activly hunting enemy nightfighters, both near their airfields while actively hunting? Mossies hunted GE nightfighters over GE. GE mostly hunted bombers and hoped to survive the Mossie. Who is the better hunter? The wolf or the thing that hunts wolves? It's a generalization, but largely true regarding nf vs nf over GE. In the largest and longest protracted NF war in history, the Mosquito (excepting the odd 262 that only had the range to play defense) was at the top of the food chain. The occasion GE got a bite of one (and got credited with a double kill, the only ac GE awarded 2 for a single kill), but Mosquito ate every night.
And can we agree that it is likely the only NF that scored most of it's kills against other night FIGHTERS?
Or, work it backwards. What was the Mossie's weakness as a NF? Others lacked speed or range or radar or armament characteristics or agility or crew factors or extremely limited use or never matured. Name one and they all lacked one or several of the elements. Many exceeded the Mossie in some category, but there is always a "BUT". The Mossie is the only one without a "but." AND it did it for most of the war, in every theater, and did it in numbers. Oh, just as a kicker, being mostly plywood, off-angle to the propellers, it gave a lousy radar return.
What is interesting is the GE view of the Mosquito in general. They hated it more than any Allied aircraft. As a type. At least by the comments of Hitler, Speer, Goering, and Galland. Until late in the war with the 262 (and even then it stood a chance if it saw the jet coming), the Mosquito was able to overfly, photograph, or harass nearly anywhere in the 3rd Reich (day or night) and unless they got very lucky, they couldn't do a damn thing about it. Hell of a thing, and on a daily basis. According to Speer, it was the possibility of driving off the Mosquito that was the winning argument in favor of pursuing the 280/262. And the GE attempt at more or less copying it (with the hugely expensive but unsuccessful Moskito(sp?) project.
Maybe I am missing it, but how is this a hard call?
P.S. This is just me spouting, but does anyone else get tired of all the "almost" GE aircraft? It's a big thing to develop an aircraft to an operational state, train ground-crew specialists, accumulate spares and repair tooling, and then run whole thing halfway across the planet. You don't do it with "maybe" aircraft. But if the war is in your backyard, what is to lose? And how much easier is it to "give her a go" hoping to chance into a home run? Getting it into combat is as easy as getting airborne.
Imagine the whole thing turned around and let the US aircraft into the war with unsorted aircraft like the GE did. So the story would be the incredible ME-29 Superfortress in 1942, the canard fighter (Ascender? Sucked but excellent candidate for "Secret weapons of the USAF" bs), the canard version of the P-80 (drawn-up in 1939, another secret weapon candidate), the P-61 in the war 2-3 years earlier, the P-80 about the same time as the 262, the Bearcat in 43, the Tigercat in early 44, Griffon-powered lightweight Mustangs, P-82. How about the FG Corsair? (On that note, the GB Corsairs flew in the ETO off carriers vs GE. Yes, it kicked ass). Suggestion for a new topic? Corsair vs P-51 over Europe. Corsair had legs....
OK, flying a Cub tomorrow if weather gets better. Need sleep.