Emm we have this chart from RAE
It clearly shows that the Spitfire MK I has better sustained turn performance throughout the speed range than the Bf109E3. It also shows Max sustained G of the Spit as 3G whilst the max sustained G of the BF109E3 is about 2.3G. With the Spit I weighing 6000lbs and the 109E3 weighing 5600lb.
We then have this chart
Which shows the BF109E3 having a better sustained turn performance than the Spifire MKI throughout the speed range. This chart shows (at Take off weight nonetheless) the Spitfire max sustained G of 3.2 g and the BF109E3 max sustained G of 3.25g
Whose chart do you believe RAE or this other thing ?