I tend to go after 51's the most.
Reason being, they are rarely piloted well. There are exceptions and I have encountered a few very good pony pilots.
I totally agree, and my stats back it up.
Plane Kills of
P-51D 64
N1K2 53
Spitfire Mk XVI 39
I know within 5-10 seconds of the merge if I am fighting a real pony stick or not.