Some other informations that might be useful to some:
VAS memory usage in JFK V2 is exactly 250MB higher than JFK V1. In the situation of the two posted screenshots, FSX with JFK V1 took 850MB of VAS, while JFK V2 took 1.1 GB. There are no AI in that screen and it's a default airplane, but of course (all else being equal), what we are interested in it's just the *difference* between V1 and V2, and it's 250MB. This is DX9. With DX10, everything goes down. Overall, is FAR less than KLAX or CYVR.
Why VAS is higher in V2, and yet the fps higher too ?
As usual, the answer is always "there's no free lunch": the FS8/9 code is clearly slower than native FSX code, but it's also more compact. Of course, just being compact in memory, doesn't necessarily mean being faster, because to translate FS8/9 code into actual graphics commands, FSX has to do much more work with the CPU than when running FSX code, even if the FS8/9 code is smaller.
The FSX native code and the way the textures/shaders are made also means the scenery takes more GPU memory but, since under DX9 the GPU allocation is copied into the user RAM, the more a scenery uses the GPU, the more VAS will use too. That's why it's best to use DX10, when you have many add-ons running together.
So, by getting rid of FS9 code, you trade some memory for performance, and I'll take fps any day, especially at New York.
If you are short on memory, there are several of solutions to try to recover it (using DX10, using less-memory hungry airplanes, lowering the textures resolution to 2048 or even 1024), but if the scenery is slow, because it's done with FS8/9 code, there's simply nothing you can do about it.