The only reason to select an allrounder for the fourth seamer (as far as I can see) is that he provides a better batting option than a specialist. Given that, then IMO there's no way MacDonald can be left out for Watson. MacDonald averaged almost 50 with the bat, Watson averaged an undramatic 33. And while it's true that Watson's bowling figures were better, he's not that good a bowler because he doesn't know what his limitations are. You can tell because he's always trying to bowl fast and sacrificing accuracy, and trying to bowl scorching bouncers which just go to the boundary. So someone like Watson will never IMO be as good an allrounder as someone who does bowl within his limitations- the Moodys, Ervines, Hopes' and, yes, the MacDonalds.