A classic way of comparing Kallis and Ponting is to look at how they were faring at the very end in their respective last tests.
In Kallis's last test against India in Durban, it was a must win situation after the infamous 458 chase draw in Johannesburg in the previous test. Now in that chase of 458 Kallis started brilliantly, playing his hots and racing to 34 of 36 balls, before being sawn of against Zaheer Khan, while getting massive inside edge into his pads (No DRS thanks to BCCI). This time around, he was more cautious and constructed a painstaking 115 to lead South Africa to massive lead and to an eventual comfortable win. While he was batting however, the usual class of dullards and Australians were all: " WTF is he doing? WhY iS hE sOoO sLowww? Lolz, he is turning the match into a draw, just watch. See this is why Ponting is soooo much better. He wOuLd hAvE pLaYeD hIs sHoTs!!"?
Flashback to a year earlier in Punter's last test (That's right, he lasted a whole year less despite supposedly being on a whole other level with the bat ?) against South Africa in Perth, and we see what he was actually capable of doing by then. In his first innings, he gets totally dominated by Philander and trapped LBW for 4 because his technique just wasn't good enough anymore with his declining reflexes. In the second innings, chasing over 600, he "decided to play his shots™", scored two streaky boundaries before being done by Robin Pieterson of all people. Trying to play an aggressive cut shot, but only getting an edge to slip (And getting caught by Kallis!) and walking of as Australia wound up getting marmalized, losing the test and the series.
To me, this was a microcosm of how they were viewed through their career. All context about Kallis's batting situation being ignored in order to berate him for supposedly letting his team down by scoring too slowly, while claiming Ponting was so much better because he "played his shots™". This while Ponting's failures in his last test (And last few years, TBH) were glossed over and he kept being put above his station by the Aussie cheer squad. Oh, well, at least Kallis proved he was superior in the end.