I remember Maugh being a pretty aggressive batsmen for the 90s so I verified JK's SR during Waugh's career and Kallis has a SR of 69 compared to Waugh's 76 with an average 3 higher. Considering the spectrum of total scores and the fact the SRs was lower back then, that's a very significant difference in SR. Also, the difference in batting position and Waugh playing in the early 90s as well more than explains the slight difference in average. Kallis's SR increased into the 00s.
Also worth noting that Waugh was absolute dynamite in general in World Cups and his SR in them is significantly better despite playing in much lower scoring WCs on average. Kallis had some very slow World cups early on and only has a half ok SR in his last 2 WCs when everyone also who was a decent batsman was scoring much quicker anyway.
Kallis's SR in his first 3 world cups when batting hasn't quite exploded leaves a lot to be desired:
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Waugh:
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Overall, Waugh was a far more explosive batsman who delivered more consistently in crucial matches IMO. Consider the 1996 WC where Waugh was Australia's best batsman nearly every match and had one of the greatest world cups ever. Kallis never came close to something like that even in that one decent WC he had in 2006/07.