When flying a slow plane u re most of the time starting in a disadvantage position so they are really good for learning how to manage and reverse E. Im no expert either but the average pilot in AH makes so many misstakes in combat that they can be beaten on a regular basis even if u are in a Brewster and meet them 1v1.
But i still claims that speed is the single most important factor - if u know what u are doing. If u dont u die no matter what plane u are flying.
And there's the flaw: flying slow is not in any way an inherent disadvantage. Flying slow is only a disadvantage when the opponent is forcing an energy fight in the vertical (or if you're trying to escape a fight, but that's not really the context here).
The easiest way to kill aircraft that run (such as the P-51, Me 262, D9, etc.) is to get in front of them and allow yourself to be slightly slower.
Again, people say the word "slow/slower" without understanding it's not really a negative attribute. It's only a negative drawback in a specific set of scenarios, much like not being able to turn is a drawback only in very specific scenarios.
I'd rather have an LA-7 or D9 all day long instead of a Me 262, despite the fact that the 262 is faster. Why? Because despite being slower, they're more versatile.