The larger the number of planes in the furball the more speed and roll becomes dominant over turn radius. In 1vs1 very small turn radius can be utilized to stay inside the other plane's circle, but in a multiple engagement you cannot position yourself inside everybody's circle. A furball is a series of random encounters and a slow plane turning on a dime is just a stationary target to shoot down for someone buzzing by at 350 mph.
The brits learned their lesson when the first 190s showed up. From the spit 9 and on, speed was the major consideration and turn ability was the first to be sacrificed when needed.
