Slight is the word and I'm sticking to it.
Compare the P40, P47, or other such tugboat compared to the Spitfire 8 and THEN I may increase the severity of the word in which I use to describe the difference in climb/speed. Otherwise, the term sticks when comparing the Spit 9 and 8.
Thanks for providing the charts though, they are lovely to look at. Too bad they only show the hard numbers, eh?