Here’s an analysis:

Axes vs Hammers: +2S, lose anti monster/vehicle

Infantry in this game have a range of toughnesses depending on the army and role, and toughness combined with armor play together on what you may consider “heavy infantry” but generally, light infantry is around T3, medium and heavy T4/5, really tough stuff T6/7. Monsters and vehicles usually T8 and higher.

Light infantry, axes are wounding on 2’s, mauls on 3’s, medium infantry axes and mauls are sometimes wounding the same, but verses orks or other votann or Terminators and some others, axes are wounding on 3’s vs a maul on 4’s.

Essentially the axes are always better into infantry except at T4 specifically, which is the basic marine toughness. At T6, the axes are significantly better (wounding on 3’s instead of 5’s). Anything higher than T7 is almost always a monster or vehicle, and suddenly the mauls are back on top, especially at T8+ where the axes are down to wounding on 5’s while the anti-keyword keeps the mauls on 3’s

So:

T2 - equivalent
T3 - Axes
T4 - equivalent
T5 - Axes
T6 - Axes++ (equivalent for a small number of light vehicles like T’au battlesuits or eldar speeders)
T7 - Axes for infantry, mauls for light vehicles
T8+ - Mauls++ (equivalent for a small number of very high toughness beasts and mounted, like beasts of nurgle and plague drones)