Both Wasim & Donald were some of the greatest fast bowlers in their generation, along with McGrath, Ambrose, Walsh, Waqar, and Pollock. Even though all 7 of these bowlers have world-class stats and picked up plenty of wickets, the truth is that their own fraternity is likely to choose Ambrose, McGrath and Wasim as being a bit more special than the other 4. The likely reason is that the 3 of them transcend stats with some of the most memorable performances for their teams in their era along with big-match presence, and superstar persona. These are some of the things that transcend traditional stats. How many ex-cricketers who actually played with or against these bowlers have chosen Waqar over Wasim, or Pollock/Donald over McGrath, or Walsh over Ambrose on bowling ability alone?
On the original topic, if the assumption is that this test could potentially be played in any of the 7 (or 8 including SL) major test-playing nations, and their own team would have a team of similar batting, bowling, and fielding ability, I would pick Wasim Akram, as he was lethal with the old ball which is important in the subcontinent (though Donald was quite good because of raw pace), and he's still very capable with the new ball as well. I'd only pick Donald if the match was in SA or against England - a lot of Aussie and South African cricketers used England as a punching bag in that generation and got loads of wickets and runs against them. English batsmen for whatever reason did better against subcontinent teams.