The problem with these threads, regardless of which plane you like, is that it always comes down to "those guys planes fly better then the plane I like. Why was mine porked and why is theirs uber?"
That doesn't apply to everyone who contributes, but there are enough folks who beat the subject into the ground that it loses focus.
Nath certainly has the skills in the arena to talk about the planes, but even he throws in-
"In the past 2 years or so it seems like all the allied planes have been increasingly made easier to fly (incredible almost anti gravity, turn radius increasing, little drag flaps and cockpits with very little obstructions) while axis planes (specifically the LW fleet) have only become worse."
It's the old implied Allied conspiracy at work.
Is it possible that HTC have refined the models towards a better representative version of the particular bird?
Think about the Spit whines about the new Vb vs the old Vc. Seems like the 'Luftwhiners" got their way on that one, if you want to believe in conspiracies. I don't buy into that. To me, and I'm a Spit history fan, HTC did the right thing making the one Spit V variant we have a more representative version from 41 instead of a later LF Vc. Just doing a quick count, I could argue forever on the Spit V as there were at least 39 different wing, engine etc combinations that fell under the label Spitfire V.
Probably not realistic to expect HTC to produce all 39 versions though, even thouugh a late 43 clipped LFVc would mop up in the low alt world of AH. And of course they could carry 4 cannon! I love that one. I've yet to find anywhere where a Spit V pilot would have wanted to go into air combat with that much of a weight & performance penalty. The only use was in ground attack in Italy where there was no real threat of air to air. All I see when I see the request for 4 cannon is that guys want the hitting power for easier kills, and aren't thinking at all about the reality of it.
Ultimately it comes down to the game having the best representative version with realistic options. As for performance, I have to believe that Pyro and the guys are using the best info they can get to make it as accurate as possible. It's not like they don't have lots of help whether they want it or not
I don't believe they are slanting the game towards the Allies.
It might also come down to adjusting to the FM and getting the best out of the bird you like to fly.