Aces High II uses dozens of vectors, such as lift points and drag points. For instance, each wing has many of these lift points at which are calculated the lift based on the speed of the aircraft. Or something like that. Here's a picture.

IL-2 has no such thing. Contrary to what MiloMorai says, IL-2 does use vectors (currently, all flight simulators do, although the unreleased Knights of the Sky by Gennadich is supposed to be using fluid phsyics, which will be better). However, IL-2 only uses the traditional four vectors, which are lift, drag, weight, and thrust. That makes for a very, very unrealistic flight model, in particular the stalls and the drag. Aces High II's dozens of vectors make it dozens of times more precise.
You can see irrefutable proof that IL-2's stalls are terrible wrong by taking up a real airplane and stalling it and by going to Zenoswarbirdvideos.com and observing how the real fighters stall in the training video. If you're blind, the narrator even describes them. There's no excuse for not realizing that the IL-2 stalls are simply wrong.