I've not put a set of callipers to either the AFV kit or the Academy.
But I do own both and I'll share my impressions.
Please bear in mind this is my opinion only.
The AFV kit is shorter than the Academy.
The AFV kit did a better job with the drive sprocket and idler wheel.
The AFV kit doesn't give you anything to cover the gun mantle with.
The Academy kit is taller than the AFV kit.
The Academy kit has those nasty motorization holes to fill.
The Academy kit has a raised area around where all the tools need to go.
The Academy kit does include the "covered" gun mantle.
The Academy kit gives you more options to use for the Hellcat, ex: Muzzle brakes vs no Muzzle brake, etc.
Somebody has the height wrong, but I don't know which is right. For my money, the AFV kit captures the low, sleek look of the Hellcat better than the Academy.
Either one is suppose to build into a nice Hellcat.