Perking planes, I believe degrades from the positive marketing aspect of the game for beginners. Brand new players aquire very few perk points in the first few weeks of participation but have to go against.
the A-team with the High End planes, and get shot to pieces, frustrated and I'm certain many quit. I think ENY does what it is basically supposed too, but could use some tweaking. Although with something as complex as this, there are holes in any process. perk points don't keep most veterans from upping a plane. With a steady supply coming in and a mass banked, So maybe perking is not the best solution, changing ENY may be. I went 26 for 7 Yesterday with an F4U1 " ENY25". The losses 3 collisions 2 ditches 2 abshuesses, 1 from a lanc and 1 from a Marauder. And My K/D ration is rarely much more than 1to1. 3 victories were 1 Razorback -11 and 2 Jugs a -40 and an M. Also virtually all my 262 and 234 vics are with P47s and Spit XIVs.
Its very likely the opposite. Not perking planes degrades the new user experience.
Item progression is an important part of game development and provides goals for newer players that keep them interested and in game. Providing every item to a player immediately is one of the worst things a game developer can do. The reason for this is simple - if you provide a player in a fantasy mmo with 10 swords of varying power the player will always choose the most powerful and will miss out on developing their skills with the other 9 swords. The player will get bored (nothing to acquire or work towards) and leave.
EvE online is a good example of item progression. I played with for 15 years. You start out with almost no skillpoints and only able to fly a frigate, the remaining other hundred or so ships can take weeks to a few years to be able to pilot. EvE has incredible player retention because of this.
In AH if you give new players a Spit V, Spit 8, Spit 9, Spit 14 and Spit 16 you'll find most players will likely just use the 16 (its the latest) and will fail to learn or try the other spits. Getting access to a new Spit as a progression goal is non-existent.
Most new players in a Spit 16 will be slaughtered as easily (or more easily) than if they were to use a Spit V or Spit 9.
The same goes for most other earlier versions of planes - against any vet you're likely better off in a early war version with its better turning ability if you're a newbie because that's what most newbies are going to do, turn fight.