Good 190 pilots can beat bad Mustang pilots in a turn fight in dcs. But most of the time the Mustang turns much better, especially with flaps. Flaps seem to help a lot in dcs for not much of a cost in energy. Same thing with 109 vs spit. In a minimum radius level turn you can outturn bad spit pilots with 2 stripes of flaps. Same with Mustang vs 109. Most of the time with between 1 & 3 notches flaps you can outturn most 109 pilots.
I know the flaps thing was discussed here somewhere before but can't remember how it ended. I think David & Mad tested it to the conclusion that basically you have more of an advantage the more flaps you use in dcs, and the cost in speed/energy is not enough to make it worth keeping them in.