Moeen Ali generally bats at 7 or 8 for England in test match Cricket, but in the first Ashes game at Gabba, the England think tank decided to push him up to no. 6 which was quite a surprising move.
Also someone who is batting at 7 has got to have a lot of big shots because a no. 7 batsman often finds himself in the position where he has to play with the tail-enders and in order to make the most out of the situation; he has to play the big shots too.
Comparing the big hitting abilities of Moeen and Bairstow, the former is slightly ahead on that front. Bairstow can of course play the big shots too, but Moeen’s range of shots is a little wider than him and he strokes the ball more sweetly than Bairstow as well. So that makes him a better fit for the no. 7 role.
Bairstow, on the other hand, is much tighter than Moeen. He has got a good, solid all round technique against the fast bowlers, can play vertical as well as horizontal bat shots and is never hurried by pace and that’s what you want in a batsman who bat at 5 or 6.
Of course he is a keeper and you don’t want him to be batting up the order at maybe 3 or 4, but many keepers around the world bat at 6, Bairstow himself has batted at 6 in the past. So the fact that he is a keeper must have nothing to do with his demotion to 7. It was very surprising and even illogical to some extent that he was demoted to 7 at Gabba and England would like to reconsider it ahead of the 2nd test.