I'm leaning towards the P-40N-5-CU...
As to the P-40F... Variations in performance from test to test were commonplace. For example, the Navy listed the maximum speed of the F6F-5 at 376 mph... However, Grumman and TAIC tests clearly demonstrate that the F6F-5 could handily exceed 400 mph in WEP and around 385 mph in MIL power. In Aces High, the F6F-5 does 384 mph at its best altitude, but that is much higher than most fly in the game. Thus, the impact on the game is virtually nil.
Last evening Gnat and I played rat race in P-40Ns in the TA.. I hadn't flown the P-40s in combat since the update, and I found that they are very prone to snap rolls if the pilot is heavy handed. Flaps are useless in a dogfight, so it's a mistake to use them for anything other than tightening up coming over the top of vertical maneuver. It took me about 10 minutes to get a good feel for the P-40s, and still I had to counter the occasional tendency to snap roll. However, the P-40C is a vast improvement over the P-40B and the P-40N can, if flown carefully, threaten many fighters deemed more maneuverable. The P-40C will out-turn (flat turn on the deck) all of the other P-40s with relative ease. The biggest handicap for any P-40 is that they will begin many fights at a significant E disadvantage.