Well, that all gets really complicated really fast.
Let's compare two aircraft of roughly same engine power, mass, and wing chord profile - only difference being that the other one has more wing area; for the sake of exercise let's keep the wing's aspect ratio also same, ie. chord length increase is proportionally same as wing span increase.
An aircraft with smaller wings has less parasitic drag.
But it has higher wing loading, which means at the same speed it has to use higher angle of attack, which increases the drag.
Both aircraft, however, have a certain optimal angle of attack at which the wing produces the least amount of drag.
Then, their optimal cruise speed is when they are flying at exactly this angle of attack, and the lift is exactly enough to counter the aircraft's weight.
For the aircraft with smaller wing, this optimal cruise speed will be higher than the aircraft with larger wing. What this means is, basically, that the smaller wing aircraft is better optimized for high speed flight and will achieve better efficiency when flown at higher speeds... and will reach higher top speed at level flight with the same thrust output from the engine!
That last part is actually pretty elementary physics. The top speed of any object is achieved when the power output equals friction/drag losses.
When the power output remains constant but drag coefficient reduces, then the drag losses are equalized at higher velocity.
However, things change drastically when these aircraft are compared in high angle of attack situation. At same angle of attack, the aircraft with larger wing will produce more lift and therefore turn better. There are also other, secondary effects such as better acceleration and better climb rate, which both very much explain why lower wing loading typically makes "dogfighting" easier compared to planes with high wing loading.
This does not necessarily correlate with combat effectiveness of the aircraft. The benefits gained in "angles maneuvers" are lost on energy maneuvers. The aircraft with smaller wing will accelerate faster in a dive, it will have higher dive speed limits, it will be more stable at high speeds, and it will lose less energy at dives and zoom climbs as long as angle of attack is reasonably small.
Of course, this is idealized comparison. There are not many examples where these conditions apply. One example that comes to mind is Ta-152C vs Ta-152H-1. In this case, the Ta-152C had smaller wing and Ta-152H-1 had larger wing. However these aircraft differed in other ways; Ta-152C used the DB603LA engine, whereas the Ta-152H-1 used Jumo 213E engine. Additionally the H model's long wing had much higher aspect ratio and thus was better optimized for high altitude flight due to lower induced drag, which is a different form of drag than parasitic drag...
However, comparison of these aircraft in IL-2 largely corresponds to what I just said. The Ta-152 H-1 accelerates better, climbs better, turns better, and at high altitudes it performs quite a bit better.
The Ta-152C has pitiable acceleration and climb rate, turns like a hippo in a bath tub, and top speed is puzzlingly low (I have some suspicions regarding the DB-603 engine model), but it definitely has higher dive speed, dive acceleration, and it retains energy quite well once you get it really going. It also offers excellent stability.
Which is a better airplane would depend entirely on what you were doing and how.
Wing loading of aircraft varies with g-loading, but typically it's expressed in level flight (1g acceleration), where it can be expressed in mass/wing area which colloquially is understood much better by people, than the actual implications of "wing loading".
If you REALLY want to get into it, wing loading is actually expressed in units of pressure. It is, quite simply, the aerodynamic lift force produced by the wing, divided by the area of the wing.
What does this means from the aerodynamic perspective?
As an aerofoil passes through air, it basically does work on the airflow to create pressure differential between upside and downside of the wing. These pressure differentials generate the lift that is used to counter the aircraft's weight.
The pressure differential is not constant over the wing; at some places it's higher, at the edges it's lower. However, if we were to average the pressure differential over the wing, it would turn out to be exactly the same as wing loading: Force of aircraft's weight, over the surface of the wing.
Why then is smaller wing loading preferable? Because the smaller wing loading means your wing needs to create less pressure differential.
Less pressure differential means less work done by the wing on the airflow - which, incidentally, is one source of drag in airplanes.
This is, of course, quite a bit simplified and it would be better to draw an image but I see this represented very, very well in IL-2. FW-190 included.
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