Stephen Bungay has a chart of turning circles in his book "The Most Dangerous Enemy". It looks to me as if the turning circle at sea level for the Hurricane Mk I is about 660 feet versus about 690 feet for the Spitfire Mk I. (see attached) Great book, I highly recommend it!
I’ve been reading Group Captain Colin Gray's autobiography "Spitfire Patrol". There are some interesting passages related to this thread's topic. Another great book, I highly recommend this one too! Gray flew both Hurricane Mk I and Spitfire Mk 1 in combat and wrote:
"There have been many arguments about the relative merits of Spitfires and Hurricanes, particularly in relation to the mark 1 versions used in the Battle of Britain. As one who has flown both in action, I have no doubt that the Spitfire was superior by quite a margin. It was some 30 to 40 miles per hour faster, climbed quicker, and had a higher service ceiling. Being lighter on the elevators it was quicker and easier to manoeuvre, and contrary to general belief it could out-turn a Hurricane." (see attached)
"The problem of manoeuvrability was of prime importance in enabling one to turn inside the enemy, certainly in fighter versus fighter combats, and thus to get a shot in when on attack, or avoid being shot down when on the defensive – and here the British aircraft had a decided advantage in my experience." (see attached)
Though a bit off topic, though none the less of some interest, Gray also made a rather blanket statement regarding Spitfire and Me 109 turn, in this particular instance describing a Spitfire IX - Me 109 G2 combat which occurred in North Africa during April 1943.
"Just as I completed my turn I saw another aircraft coming towards me at high speed, as he flashed past I recognized a 109G2. He obviously recognized me as hostile because he immediately pulled up into a screaming left-hand turn and attempted to dogfight. This was his big mistake because there was no way a 109 could turn inside a Spitfire." (see attached)
Mr. Gray flew Spitfire Mks I, II, V, IX, XII and XIV in combat and is credited with 27.5 victories, all in Spitfires. He fought over Dunkirk and through the Battle of Britain in 1940; commanded a Spitfire IX squadron in North Africa, then was wing commander during the invasion of Sicily in 1943; and led a Spitfire XIV wing as Wing Commander Flying over France, Belgium, Holland and Germany in late 1944. He earned his say in my opinion and I’ll not be one to take issue with his experience.