In normal DnD rules, if you crit, you had one weapon damage die. So a greataxe does 2d12 on crit, while a greatsword does 3d6 (confirm by Sage Advice, but I don't know how it is coded in this game). So a class like the barbarian, who can add extra dice to a crit, will want a greataxe.

But if you exclude crit, I guess a greatsword would be more consistent.