In years past I read a lot of Keith and O'Connor and while both seemed very knowledgeable the main differences I noted were their choices of rifles for big game. O'Connor felt that if you had a 270 and 375 you were ready for anything the world had to offer; Keith vehemently disagreed and felt that you needed bigger bores for any of the 'big 5' and bigger than the 270 for medium game. I do recall one article by O'Connor where he stated that a 270 or 30-36 was perfectly adequate for lion or leopard. Having read a lot of safari articles, I doubt that he could have gotten too many PWH's in Africa to agree with that. Also having received personal answers from both these gents the ones from O'Connor were grammatically perfect and these from Keith needed a lot of polishing up. Both , however were very excellent and I treasure their books, especially those from Keith.