However, (again digressing from the topic) I feel that both Warne and Grimmett were slightly better bowlers than their overall bowling averages suggest, respectively.
Warne, because I saw him playing so many times that I know. Grimmett, because I've read so much about him (and so much written by him) that I know he was a master of legspin bowling. The way he used legspin and googly and the way he used flight were all so planned and well thought-out that I was moved when I read him first. The way he worked out the weaknesses of different batsmen was amazing. And the stories about his practice sessions are so astonishing (the dog story and the coin story comes to mind). He invented flipper and quite a few variations of flipper. The best part about Grimmett's (and O'Reilly's) usage of the googly was that their googlies generally pitched on the same spot where their legspinners pitched. So, if a batsman couldn't read the ball from their hands, there was no chance that they could read from the trajectory. Nowadays, there are so many spinners whose legspinners would pitch on the leg stump and their googlies would pitch outside the off...makes it so easy for the batsman from the trajectory itself. I love how Grimmett taught Ashley Mallett the importance of flight through the example of the bridge and the manhole. Grimmett was devastating against the technically weak batsmen, mainly because of his different variations of flipper. No wonder that some people hold his record against SA and WI and weak FA sides (10/37 comes to mind) against his all-time greatness. However, he used less of flipper and more of his stock ball and wrong-un against better batsmen. Grimmett probably had more influence on the upcoming legspinners than O'Reilly himself, primarily because of his scientific approach and extremely intelligent way to analyse the game as a bowler. No wonder that Ashley Mallett called him the Bradman of Spin. Grimmett is one of the two players who took more than 100 wickets debuting after the age of 30, and still the only one to take more than 200 among such players. At last, he was dropped from the test side at the age of 44 after a series where he was the most successful bowler by far (it must be known that he wasn't the best of friends with Bradman). He continued to be extremely successful in FA arena. He was a man with supreme ego, and as the story goes, when he was recalled in the test side a year later, he declined the offer. He could be the first player to cross 300 wickets too if he wished, who knows? The writings about Grimmett, and the writings by him, are probably the best literature one can find about spin bowling.