Bro use an axe, when you get enchants, use your sword, and get smite on the axe, but ehen at that stage of the world where your tools and/or armour is enchanted use the axe.
It depends if the only tool I have is an ax and a hostile melee mob appears I'll use my ax for that and harvesting but if I have a sword I'll use that first for fighting
it depends. For mobs I usually use an axe because most mobs are pretty slow and some die to one axe crit but for players I use both (a sword to combo them or an axe to crit them out if their armour sucks)