I'vs got a perfect answer for you.
The best metric should be measuring the specific energy loss rate in a turn, since actual dogfight involves such turns.
Here is an explanation:
PS = specific excess power which means how fast the jet gains/loses energy in maneuvers.
Q: Why is it insufficient to measure STR (sustained turn rate) alone to verify the energy maneuverability?
A: There is an illusion that STR alone stands for energy maneuverability. If the game adopts a wrong drag profile, and tries to compensate the higher induced drag with modified zero lift drag or engine thrust, we may see an accurate peak STR, but the energy bleed rate at higher turn rate will still be higher than the flight manual. That is determined by equations of flight dynamics.
That's sometimes misleading. Some people claim the peak STR has small error, while some other people cry for high energy loss and they struggle to recover energy. They are not contradictory. We need to check the PS loss.
Q: How to get the ps since Tacview does not show that?
A: PS = (thrust-drag)*speed/gravity = longitudinal acceleration * speed / g = longitudinal G * speed.
Just check the “longitudinal G” in Tacview, read it, and multiply it by the true air sped (TAS), you get the ps value.
Example: (these numbers are for sample only) make a level turn at true air speed of 300 knots (154.3m/s), the lateral G force is 7G, and the longitudinal G force is -1.5G, we have:
Ps = -1.5 * 154.3 = -231.45m/s = -795feet/s
Level turn rate = square root (7^2-1) * g / speed = 6.92 * 9.8 / 154.3 = 0.4395rad = 25.18deg/sec
Read the flight manual for “300knots, 25.18deg/sec” and check if the ps is -795feet/s
(We may double check if the Gs are in body frame, but that won’t affect much the result)
Q: Why using true air speed instead of mach number?
A: The speed of sound in flight manual and that in DCS are slightly different. Using mach number causes some error. The speed of sound in flight manual is about 333.5m/s. This can be proven by picking a point in the E-M chart and do the maths.