Compared to AHII, I couldn't tell you. Although, I hear the gunnery is more difficult in AHII and requires being closer than the original AH.
In that respect, Il2:FB/AEP (soon to be a PF appended to that) is almost exact. Convergence matters, and so does actually hitting the target at your convergence setting. I don't play with icons on most of the time, depends on if I'm on War_Clouds server or greatergreen... don't think either actually have range on anyway, but to get back to my point - if you hit at convergence you do more concentrated damage to a part of the airplane you aimed at. This can mean severing wings, ripping off the rear fuse, setting the fuel tank or engine on fire, blowing the plane up, etc. Also shooting up a plane while sitting on its dead six is not as deadly as it is when you shoot at them from above or below. Like if they are in a turn and you get a lead shot where your bullets will be smacking their wing from above rather than behind, this typically results in a quick burst snapping the wing off.
Long shots are possible, but not easy - and never fatal.
Flight model - all subjective really. Damage to plane parts affects performance, more likely to get into a spin with damage to the wing (if you pull too hard) and the other typical damage resulting in degraded. Personally to me, they seem very close. Don't really notice any differences between AH and Il2, except that it's harder to do the NIKI hang on prop deal because you lose aileron control at low speeds (about 30km/hr).
-SW
