War Thunder is an extraordinary game. In full realism it gives you quite deep real war immersion:
1) No enemy icons
2) No damage list
3) No radar
3) No ammo counters on many planes
4) No auto trim (no aileron trims at all on many planes)
5) No artificial horizon on many planes (with no autotrims it is a real challenge to fly in the clouds)
6) Engine may overheat (if you do not take care of it)
7) Midair friendly collisions ( love to see how two cherry pickers collide with each other trying to attack your plane simultaneously)
Put it on top of excellent graphic engine (which runs surprisingly smooth on 5 year old computer) plus the total number of already modeled planes the game definitely creates WoW factor.
As for the flight model it is pretty similar to AH in case of stall behavior modeling, though AH gives you much longer pre-stall warning.
WT community consists mostly of the people who came from World of Tanks. Their most likely impression is: "WoW we could not believe that the flights sim could be so addictive and entertaining - even more addictive than World of Tanks".
These people actually play mostly in arcade arenas though which it is not a flight sim but more like arcade shooter with rpg elements. Who cares if they have fun.
Last week I noticed 13,000+ people playing on arcade servers in peak times.
I expected that there will be much more people from IL-2 but previously many had have quite negative attitude towards War Thunder due to arcade arenas.
Now they discovering full realism servers and their attitude gradually changes to positive.
As from the point of view of former WarBirds/AH player War Thunder is not perfect game. There are a few very important things that are simply better in AH.
1) View system. AH beats WT hands down. I had to put the second mouse left to my keyboard and used it for left-hand viewing from cockpit though it is still not satisfactory enough to match AH view system. Without tracking device you can not see some important gauges on instrument panel on some planes and have a quite blind 6 view on some other ones as well.
2) Voice system. WT people use Skype
3) Plane performance modeling. I believe that AH is the best in accuracy of modeling of level flight speed, climb ,turn, level flight acceleration except diving speeds.
To sum it up War Thunder is not a direct competitor to AH and AH customers will not migrate to War Thunder but from the point of getting new customers AH is in the trouble now. There are quite obvious reasons.
1) AH doesn't create Wow factor from the first view. Neither from screenshots or from the website which looks old like Yak's cockpit.
2) WT doesn't require long hard learning period. Everybody can jump in and have fun with mouse controls in arcade arena instantly.
3) You can try and play WT for free as long as you wish and even for free you can get to level 5-6-7 quite quickly which means you can get access to not a bad planes like Bf-109F, Yak-1b, P-39Q etc
4) WT marketing is quite strong and the game is already well known it World of Tank and IL-2 communities (which are massive) while lots of people who have heard about WT have never heard about AH.