To greatly simplify the explanation, the biggest factor is called Reynolds Effect. The more air molecules that are on a wing at any given time the more efficient that wing is going to be. A wing can be shrunk down but an air molecule can't. Mass has a big factor as well. I also preach ( limited success ) that the way an airplane is set up has a huge hand in the way it flies. Think of your airplane as a symphony. All parts have to be in harmony with one another. This is where thrust angles, wing and stabilizer incidences, center of gravity and such come into play. IMO everyone should learn to manipulate these things to get the desired flight charictaristics. IMO the old " she took just a couple clicks of trim to fly perfectly " just doesn't cut it, it just shows limited knowledge.