P47 Nancy has the same engine as the Mary yet its overall performance is closer to the D11 according to the charts. Perhaps the charts measure the Nancy's performance while its loaded down with ords, because that's the only explanation I can come up with. Is there any chance the performance charts will get updated?
The charts assume 100% internal fuel, and as mentioned by Karnak, the N carries more fuel than any other Jug (90 gallons more than the D-40, D-25, M and a bit more compared to the D11, I dont remember the exact D11 fuel load). The extra fuel is in the wing tanks.
In addition, the N is heavier than the other jugs even when empty because it has larger wings and had to be strengthened to withstand the extra loads (stronger main gears, etc). Without WEP, it is the worst performing Jug, about matching the D11 in climb (because D11 is modeled without the paddle blade prop) and rolls a little bit better. The monster WEP is what makes the difference in performance to the N's favor.