If you are talking about average spitfire mkXVI pilots then lets switch that around Widewing. A decent spitfire mkxvi pilot should easily rope and despatch the average Brewster pilot. A very good Spitfire mkV on the other hand will often mix enough agility and vertical power to outfly even a well versed Brewster. The skilled mkXVI pilot would, as you say, probably lose to the skilled Brewster. But then the mkXVI is not really meant for turn and burn, its not really even a real spitfire.
Undermost circumstances, pilots being equal, the better plane usually wins. But, not always in duels. This is due to the fact that duels often favor one type, usually the more agile of the two.
When you compare performance between the Brewster and the SpitV, you find that the Spit barely out-climbs the B-239 using WEP. Without WEP, the Spit is in the hole. Speed goes to the Spit, as long as it has WEP. Turn and roll rate go to the Brewster. In short, the SpitV pilot will have his hands very full. The Hurricane Mk.I is outclassed by the Brewster. So is the Mk.IIC, which means that the SpitV may be in over its head in a Co-E, Co-Alt match-up. We'll have to try that match-up some day.
I did duel a good stick who flying the 109F... He never hand a chance against the Brewster. Dumping flaps only sealed his fate. You have to fight the Brewster like it was an A6M2. Stay fast, avoid turning with it for more than 90 degrees. Don't even consider using flaps.
My regards,
Widewing