In Scenarios, stallfighting turn performance can matter, but many things are boosted in importance in the Scenario environment such as speed, snappy handling at speed, ammo duration, ability to get to high altitudes, and toughness of the aircraft. Also, the planes are fighting their historical opposition, and that matters (like P-40 vs. Zero and not P-40 vs. Spit 16).
The fights tend toward many on many, starting at higher alts, and without as much knowledge of what is around you and what is coming in (since dot radar usually isn't present) -- so situational awareness and group tactics have a huge impact.