Pretty sure if I was the SA captain, I would pick McGrath over Pollock, assuming Donald isn't around.
The problem is that cricket isnt just numbers on a spreadsheet. You have to remember the context.
McGrath and Pollock were their respective opening bowlers of their teams. A relatively small difference in the output of a pace bowling spearhead would have a massive difference on team series results.
McGrath has nearly twice as many fifers as Pollock. If Pollock took wickets at the rate McGrath did, he would have something like 70-80 more wickets in his tally. That could mean the difference between multiple series victories in places like Australia and England where SA couldnt win over the course of a career since the opening bowler has the most impact.
Pollock's batting at no.8 was no doubt very useful but even over the course of his career I don't think it mattered as much as McGrath's sustained excellence which had such an effect on Australia that it was noticed even when he wasn't taking wickets.
If Pollock batted regularly at 6/7 it would have been a different case for me since that has more impact on match results. Flintoff who averaged less than Pollock but batted at 6/7 was more of an impact bat IMO.
Hence when it comes to Hadlee and Imran, as bowlers they are hard to separate but Imran the bat over his career made a lot more difference to Pakistan than Hadlee did with NZ as Imran was regularly saving Pakistan after top order collapses.
I'm well aware cricket is more than spreadsheets thanks. I've pointed that out to the 'Southee > Bond' brigade recently.
South Africa didn't lose because of Pollock, they lost because some sides were too good for the Pollock/Kallis axis to keep them competitive. You go tour 00s Australia with Boeta Dippenaar, Jacques Rudolph, Nicky Boje and Andre Nel.
There's a general trend in sports to blame star players for not doing more in losses when the problem is usually their team mates could be better.
Batting at #8 is a huge advantage. Daniel Vettori being the most recent example of the premium #8 keeping NZ out of associate status along with Ross Taylor. To minimise it is silly, and given Imran and Hadlee often get picked in ATG exercises as the #8 because they can bat I think everyone understands this when we don't mention randomly denigrated South African cricketers. You'd think Pollock averaged 28 with the ball the way people carry on about his bowling.
Without scorecard browsing Pollock's batting kept South Africa competitive in at least one odi series I recall against NZ where he almost won them games from nowhere.
Pollock probably sacrificed some bowling time to be a better batsman, and no matter which way you shake it he is an ATG pacer, one of the very very best ever bowlers to live. One would need to go full CricketWeb Brain to try and deny it. Adding a very healthy batting average on top of achieving something most test bowlers never do with more time investment just makes Pollock an unfair cricketer. He is a very special player and people always seem to hyper focus on Shaun Pollock 2008 rather than Shaun Pollock, ATG pace bowler.
If he was Australian, Indian or God forbid English (with 800 test wickets to match) we'd never hear the end of it.