Personally, I would opt for Ceruledge, since Bitter Blade is a draining move and can heal, but Armour Cannon can lower Armarouge's defenses, making it easier to kill, since its defence and Sp.D aren't that excellent to risk a drop. It can also be revenge killed by aqua jet after a resisted switch-in to Armour Cannon. Ceruledge has Bitter Blade to heal off damage and is more difficult to kill with aqua jet.
Ceruledge is also slightly faster (85 base speed compared to Armarouge's 75). Ceruledge also has swords dance in its base moveset (no tm/hm/move tutor) compared to Armarouge's calm mind, allowing it to set up to +4/+6 offensive faster than Armarouge. Ceruledge's typing is also better, with 5 weaknesses, 5 resistances, a quad resist, and 2-3 immunities, depending on if it has flash fire or not. Armarouge has 5 weaknesses, 6 resistances, and 1-0 immunities, depending on flash fire. More immunities are better than less.
